I've had this happen a few times now, both on my Dyno 115 and my JP 102, so I'm doing something wrong in setup and technique.

I feel pretty secure in the straps going over light chop, but sometimes when heading out through waves while on plane when the fin leaves the water, my rear foot comes out immediately and I crash on the landing. Last one was painful because I did the splits. Could have been a lot worse.

I've had my foot straps set up to be large enough to be able to rotate my leg, while in the strap, and touch my knee to the board. I think Ben Proffit was the one that showed that tip. But, maybe it's still too loose? Maybe I am not gripping the board too well with my rear foot by curling it? Or maybe there's something else I need to be doing? I'd really like to not keep coming out of the rear strap as it spooked me on one of the rare windy days here.

This video isn't the best view because I had the camera on the side more able to catch the wave rides than the ride out, but you can also see how the nose gets pushed up and leeward after coming off the wave at the end because I was then only in the front strap, then crashed.

For foiling I try to use the rears unless going downwind, and on the race foil they are setup to just get the little toe in like a slalom setup.

I think the dyno has them as narrow as I could make them. I'll have to double check on the JP, but I've come out of both.
I'm pretty forward on the wave boards when shlogging due to the volume but definitely get more out and back with a straight front when I need the speed. If anything it looks like my weight may be too far back?

Severne enables a wide strap setting as the inserts are at 160mm not 150mm like everyone else. You need to rotate the plastic bit inside the strap to get them tighter.
Dunno about being able to rotate the foot like that. Its risking being able to stick it all the way thru up to your calf in a bad crash, and if that happens in waves you're dead.

strap snug side to side, but the toes poking out, jam it in hard. Then if its still coming out its technique.

I wear booties full time. I want to feel the sides of the strap slightly and see my entire toes. I doubt my knee can contact the board.

I disagree with having your weight too far forward, the rear foot is mostly just steering a modern waveboard.

^^^ but spins out all the time that he is not in the air.
I do agree with you its technique or setup (ie: the answer is not big straps ) - but you can't tell someone to simply weight the back foot
More finicky than that and hard to say without seeing

Hopefully, I'm not so far off :D !!

Need to lean towards the wave more, put all of your weight in the harness and absorb the wave shock.

What you're doing in the video is basically is uncontrolled jump. Your sheeting out and causing the board to head downwind.

So either you need to be more aggressive, push and pop or relax, lean upwind near horizontal and absorb.

Remember that when off the wave and in the air there's no more fin traction so all side load needs to disappear.

Manuel7 said..
Your sheeting out and causing the board to head downwind.

I dont think he is sheeting out, if you keep the boom angle to the horizon in mind it stays the same. It looks like he is sheeting out when the nose of the board heads downwind, but I dont think he is.

I find it difficult to understand what's going on here.

What feels best to me as far as rear foot goes is to set it at 45 degrees with the inside of my foot "glued" to the front part of the strap.

When crossing the white water you want to press hard on the back foot to clear the nose and drive the board forward with your front foot.