I have no problem making a loop more than tight enough with elevator only and on low rate, maybe 50%. It's making big, round, majestic loops that I'm working on and my challenge is getting the size, trim, airspeed, power, etc. just right so that the plane doesn't waffle between positive and negative when going over the top.

Now my little combat foamie, that's another story. I have a switch that will mix full elevator up to full down ailerons; I could probably cut my own streamer if I tried hard enough.