Hi all,
Not sure if this is the right forum for it, but I thought I'd put some notes together for those who are learning how to foil. It would be great to have lots of input on this, as it's a tricky thing and I think there are some BIG ticket items that, if you get them right, then things will massively improve.
I'll kick off by saying that Russ and I foiled Dorans on Sunday (when everyone else was wavesailing - good on yas). Conditions were 10-20 knots. Gusty. North west direction. Tide was full which helped a lot. It was a typical crappy Dorans day. Don't mean to brag, but we had a hoot!
We are both using the Naish Hover 122 board and foil. I found there was a lack of instructions on how to set this thing up and I relied on Russ's chats to others for ideas on setup. Here's what we came up with:
Set up the foil as far back as possible in the fin box. This seems to stabilise things. Also we were told to have the footstraps as far back as possible, but mine were in a mid/forward setting. Advice on the mast base was to also have that far back as possible, which we both did.
The rear trim foil needs to be level with the front one. I set mine with max lift the first time I used it and the foil would boil up out of the water and cavitate - impossible to control. There are maker lines on the back of the rear foil. Line these up and you should have it all set to level. For learning, I would suggest this is DEFINITELY where you want it.
Our experience: well, I found that the board erupted out of the water as soon as the sail powered up. The foil would keep lifting, so if you weren't trimming it, the foil would also pop - followed by a nose dive.
We both seemed to think that keeping mast foot pressure was good for keeping the nose of the board down, and preventing the foil from developing so much lift that it pops out of the water, and the board then nosedives (which if you're expecting it, you can recover from). So in hindsight, maybe the mast foot forward might be good for keeping the nose down. Next time...
Also, find your crappiest, oldest, most delaminated sail and rig it. I used a 2016 6m wavesail and found it developed waaaay too much power above 15 knots. Rigged a 10 yr+ old wavesail (4.6m) and it was MUCH better. If you're thinking about upgrading your sails to suit a foil, then dont. I'd suggest downgrade them first.

We found when the foil was flying, you just needed to get in the 'sweet spot' where you and the board were nicely balanced, and then just trim the sail lightly.
My tip for learning (for what my 4 sessions are worth...) - get the board planing. As you feel it lift off the water, try to trim the board (depowering the sail - and mast foot pressure) to get it to go down on the water again without losing too much speed. It might sound counter to what you're trying to achieve, but we found that getting the board out of the water is dead easy. Controlling it once it's up is the trick. And keeping the nose down is the key to that for me (and probably Russ) at this stage.
Oh, and we both found the construction of the board is a little on the fragile side. Very nice finish, but has a feel of not being particularly durable. Also, undo the screws and bolts for the foil on a regular basis - and clean. Have heard they can get bound up and tight if you leave them set up long term, and that would be potentially bad.
Again, if anyone else has any tips, I'd love to hear them.