Tried a F2 sx 81 litre slalom board yesterday,front foot was coming out of strap big-time,especially in the chop. Felt like i was sailing with only one foot in the back strap,it was so bad.

Played around with tension on strap and no difference,shame as board felt very comfortable otherwise.

Today,going to take one of my Drake/starboard straps off my sonic and see if this helps.

Not sure if it's the footstrap itself, curve of the board wall or angle of strap set.

Anyway, i reckon these Drake footstaps are awesome so fingers crossed for today.

Think Nebs is on to it, it's more about the relationship of centre of effort to centre of lateral resistance. In other words it's where the harness lines are pulling you, not how tight the straps are.
I have trouble getting my old head around this one, it's complicated geometry, moving front strap back, mast base position and boom height probably also have an effect.

feet coming out on both tacks prob means the boom is too high.
if the boom is where you have it when your on your sonic then the mast step on the f2
may be further aft than the position on the sonic.

Was there a plane flying overhead? could have been those damn Chem-trails messing with your head

Thankfully,the ptb spared us today from the particles of aluminium etc,so looking up at the ali spraying was not the problem.

Could not afford the $20 for a large Stanley star screwdriver at the hardware shop,so going to test tomorrow.

Think it's the flat contour of the wall of the f2 that is the problem,nothing to push against.

Going to try to position front strap more outward and parallel.

I do sail with nearly all my weight on backfoot,so frontfoot has little push into it,but doesn't seem to be a problem on other boards.

The sonic i76 another board i had problem coming out of.