when you said it slide you toward the tank, i was going to suggest a pants with grippers on the bottom would do the trick, but then you mentioned the wedgie issue,,, then i concluded that the corbin seat is not cut correctly to the right incline angle. Your body want to slide fwd, the seat is holding you in place and causing the wedgie.
it sounds like the problem is that the seat should be inclined BACKWARD toward the tail, and in your case, your seat might been inclined toward the tank instead, not sure if you understand what i mean,
it's like on some bikes you can adjust the seat height by raising the front or the back or both.
if you raise the front only, you wont get wedgies, thats how seats should be built, slightly inclined to the back,
if you raise the back only, you will get the crotch wedgie
so yea... it depends how the seat is cut and trimmed. it makes a huge difference!
i hate seat search phase, i'v been trying to find a good seat for my 1200gs and still no luck... my klr is much more comfortable than my bmw bike.