Tesla1856, i flew the earlier version of the Seagull Edge with a Magnum .91 slx (2 stroke). It was an excellent combination. The Magnum does not give you the problems the OS 91fx gives. It is powerful, reliable and very user friendly. Plus it gives you the option of carb mounted needle valve (where it should be) or remote mount. Also, the engine fits side mounted perfectly inside the cowl. With a Slimline large capacity Pitts style muffler (the same one labeled for the OS 91 fx) it looks good and sounds good. And, it costs a lot less than the other engines you are considering.

When you do get to flying your edge, check your elevator control response carefully to avoid excessive throw. It can give you a snap when you don't expect it. Don't ask me how I know that.

Good luck.