Still in the search for my larger sail (the H2 was sold)
I've been offered a brand new 8.8 GPS for a really good price, it needs a 4.90 mast, the only one available is a naish 75% sdm.
For those in the know, would it be a good match ?
Thanks in advance
Sean
I have rigged my 8m on a Tush (worked well), and a North Gold (needed couple of spacers in the bottom 2 cams). Think the Naish is a bit more stiff top than the North though. Hard to say, you need to rig it, they are quite stiff as well on the first rig but soon loosen up. I would predict that it will make it very very full (they already are with the Hot Rod slightly flex top masts) at the boom.
I kept this chart of compatible masts and sails, looks like yours is not a perfect match, but not the worst either
Another mast comparison chart for you.
www.unifiber.net/masts-selector
looks line Naish and HSM arent too compatible
The GPS is a hi performnce race sail and in my experience race sails need to be tuned properly for best performance.
I rigged a GPS on a Pryde mast which was supposed to be compatible. After some fiddling the sail looked ok and sailed OK. However when I tried it with a HSM it was chalk and cheese. The sail came to life, made it smooth, softer /pumpable, and rotation efortless.
Unless you can try both masts and feel happy that the sail is working to spec then I wouldn't bother. Otherrwise somewhere down the road you may end up buying the right mast and wasting your money on the one that didnt work.
I can allweays bring one over at Xmas! 
Fastest I have had from my 8 is just over 34knots.....would usually be changing down to a 7.3 in those conditions but was end of session. Rigged with full downhaul at 32cm (sometimes in lighter winds I will put it on 34 and leave a 3 cm gap to lift the foot a little to not catch on the rear straps while doing long reaches)
I set my boom to printed length (...cant remember...boom dedicated to sail so never change it maybe 206 rings a bell think 205 is the printed setting) but do let off about 3 cm to 5cm for off the wind runs.)
Lots of batten tension in the bottom without the cam, one spacer in the top cam. Any more downhaul than this and the cams stick a little and the sail needs a real off the wind shake to get the knuckle round on the lower cam which then brings the second cam round too.
I use either the middle or lower clew eyelet, still experimenting with these to be honest.
Experience with fins - I ride on Exocets RS4 mostly with this sail - 69cm, 111l. lower wind I use 40cm, medium 37.5cm, both Black Project Type R, then if I am doing some speed runs will use my Type S 35cm....this fin matches the board and sail to perfection, never spins out, and just keeps accelerating, significant speed difference with this set up. My hot sail uk team mate uses an Isonic 111l but finds the 37.5 too small and uses the 40....he doesnt get the top speeds but is a much better slalom racer with it than I. In terms of the fins, I weight 87kg, team mate 82kg, other team mate 120kg........Now the big guy much prefers the type R which are a lot stiffer at the tip, for me I find them slower and prefer the flex of the type S.
The sail with less downhaul has a massive range, I can get it going in the same wind as my 8.8 on my 78cm board, but it does lift you a bit more. I have used the 8 in 10-12knots min up to 30knot gusts, never feeling out of control but at that top end I could feel more drag (if thats possible), the sail is at its peak in 16-20knots for speed runs I reckon...with bigger gusts to bear off with.
Hope all that helps.
Okay, thanks for the input guys.
So the closest mast I may have found is a loft SDM 4.90 100%.
Seems constant curve with a flex top...
And now I read on the Hot sails website that : "Due to the camber inducers the GPS cannot be rigged on a SDM." 
That's on one page but on another it states that both SDM and RDM are ideal masts for the GPS...
bad communication ? printing error ?
Has anyone rigged a gps on a SDM ?
The seller here assures me that he has on a naish sdm and it was fine; But he's the seller !!
i ve sailed stiff top masts in CC sails . if you downhaul it to specs you ll find the boom length will be much larger, so go less DH until the boom gets closer to specs and it will be ok. the top of the sail will be much tighter that it is supposed to be. ok if your heavy/strong but you ll hate it if your light/weak...
Philn, havent measured my extensions, I know I rig the sail with max downhaul most of the time, as I always use bigger than I need really, must get out of that habit! You can try with an extra 2cm, nothing to lose other than having to knock the second cam round for that session, or let a bit off. I have found when you go past max downhaul they still sail well but wont rotate for me on port tack unless encouraged. They rotate fine back on starboard though.
You know you are at the limit with downhaul if you have to let off a touch of outhaul to get the cams to rotate easily in my experience. All that said when I first joined the team I only had a 7.3 and 6.6, and used them both in underpowered conditions with minimal downhaul still with fast runs.
Where I sail it is difficult to make minute adjustments due to the wind. I mean the wind is gusty and one run can be slow with the next blistering (for me), everything else being equal. Its also quite busy so its like playing frogger with the freeriders and kites when bearing off.
I do need to experiment with the different settings on one sail, to see how much 2cm off the downhaul slows me down, like I say though its quite difficult to do here, a more constant wind would be ideal to experiment with......roll on the Autumnal gales ;-) I have spent more time comparing different sails with the same settings (max downhaul).
Sean, I think Loft will be good, the sails come with spare cams for SDM. The specs on the website I think are for 2011 sails that didnt for certain sizes. Any problems in terms of the top cam are easily fixed with spacers, my 7.3 up all have a spacer in the top cam for a tighter fit, tried 2 in my 8.8 but that was too much. The way I see it with the biggest sizes like that is you are not going to break records, its a sail to get you on the water while you wait for the wind to increase ;-) I spend a lot more time tuning my smaller sizes (most used are 7.3 and recently 8), the 8.8 only comes out to play if I know the 8 is not enough.
If you have any real technical questions then Jeff is quick to answer on their forum - http://www.hotsailsmaui.com/forum/viewforum.php?id=1
