Hmmm, yeah I've wave sailed my Flow 8'7 with a 5.3 and it was awful actually.
I went out thinking light wind waves would be good, no straps to worry about so plenty of foot room to move around the board... and all it did was bog and drag around. It had float but wouldn't get up on a wave and surf it, it bogged a lot and became very very stiff to turn, like the tail was dragging.
(you'll understand what I'm saying if you've ever light wind wave sailed)
The board will take a rig, plenty of space to rig flip and turn pivots on the tail (no flare gybes) but the biggest turn off was the lack of speed, it really didn't want to move very quick at all.
Conditions were 3ft x-on 15knts, Flow 8'7, 5.3 wave sail on RDM.
Not going to try it out on my Speeed, and that too has a mast track.
TBH I'm not sure why the tracks are in the boards...
You may have more success on your 8'10 Flow, but I wouldn't over rig it.. max 6.0 in light wind waves would be far better than trying to get it up ripping.
Youve got to have a go, let us know how you get on. My experience has put me right off doing it again.