Maybe I'm the odd guy out, but I've always put the button between my pointer and middle finger. If the button has some weight to it, I will sometimes have the problem of it slipping, but not as bad as you describe. Usually though, it will stay in place.
I have tried the button between my middle and ring, but since I'm not used to it doesn't feel right. Reading Neffs comment about the button being below the wind though, I'll have to go back and re-examine my grip.