RE: That pesky rear footstrap
I come unhooked on occasion too. I think it's definately lack of commitment to weighting the harness. You tense up and pull the boom in a bit to counter the pull and you're unhooked.
I've been working a lot lately on weighting the harness fully and riding up and down the sweel with movement in my lower body only. The few times I get it right the chop seems to virtually disappear.
That's one thing I love about the FF/FT and bigger sails. It gives you plenty of time planing on relatively flat water to work on your stance. It allows you to lock into a solid stance which hopefully you can carry through onto smaller gear in rougher terrain.