I have some idea what you're dealing with. I've been diving my new wing without a crotch strap and, initially, the bladder was riding up on me and forcing me forward some while on the surface. I've reworked the straps and really cinched up the shoulder straps so it's quite snug and now I'm using it with a dry suit as well.
Because the dry suit is providing some additional positive buoyancy, and because the wing is strapped on tighter, I am having no problem with it riding up or tipping me forward on the surface. I really like the set-up now, after 6 dives as is. It seems that, underwater, horizontal is the natural position with this set-up. But if I didn't have a dry suit I would likely add a crotch strap to ensure the wing stays centered on my back.
Also, you do feel a bit naked initially, with out the jacket, but I'll bet you like it better in the long run. Good luck.