As others have advised, stick with convex wafers. Adding convex rings won't hurt. Goal is getting your stoma above skin level. Might be uncomfortable for a while... all that pushing down of peristomal skin.
You could add an ostomy support belt. Try the belt by itself over convex wafer. See what happens. Still leaking.. add convex barrier ring under the wafer. Put on belt. Belt will maintain constant pressure. If still getting leaks. Another idea: Using a 2 piece system with snap on bag.......Place the convex ring under the wafer, install wafer, then put a regular ring on top of the wafer around your stoma. Snap on bag. So now you have a double seal. Put on belt or try it without. See what happens. Remember to gently push and mold ring around your stoma, both bottom ring and top. Note: Use gloves when handling rings, they are sticky. It takes a few times to get used to working the rings.
After recovering from surgery, hardest task for an Ostomymate is finding a system and products that work for you.
You should consider consulting with a surgeon about revision surgery. A stoma flat to the skin will constantly cause you grief, especially an illeostomy. It's not too hard for a surgeon to pull your stoma out a bit.
After my surgery, I was pissed my colostomy stoma poked out so much. A little over a year later... I'm so happy my surgeon did this. Yeah, I gotta live with a big lump under my shirt. But I've suffered no leaks, and changing wafers/bags is easy.
Nu-Hope corporation makes many styles of support belts. They are located in Pacomia, CA. They can be ordered from your ostomy product supplier. Amazon has a wide selection of belts. I've ordered quite a few to try out. They're not too expensive. If you're active, exercise alot: Stealth Belts are good. Google "Stealth Belt" for their web site. Wearing a support belt is advised when recovering from surgery, maybe 4 months or so. It's very easy to develope a peristomal hernia. It's not proven a belt will prevent it... but worth a try. And in your case, a belt might help prevent leaks.
"Charlie the stoma" love it.
Good luck