I'm using the JR X378, it has 5 point curves , but i nulled out a couple points so it is simple linear -9,0,9 pitch curve for idle-up and -4,0,9 for normal. The throtle curve is also simple 3 point. 90,50,90 for stunt and i think something like 30,50, 90 for normal. nothing wrong with more points, its just i like things to be as simple as possible and it works pretty good. The guy who is helping me taught me to make sure top halves of the curves all match so it is easy to switch modes in the air. I like that too.
The loop is pretty easy to do, (except for being a littel scarey the first time or two) but hard to make it smooth. You need lots of positive pitch as you are heading up for the first third, then smoothly transition to a few degrees negative as you start to get inverted then smoothly transition to lots of positive pitch as you get around to the last third of the way around. Mostly you just hold the right stick back. Part of the weird thing in doing loops with a heli is it can loose forward speed and kinda get stuck at the top. Just keep the right stick back and it will flip over. not sure what to say about that. Ive made some good looking loops and some crappy ones, but at this point i can't say what i did wrong or right. its all timing i guess.
Whatever you do, do not fly a loop like an airplane. If you just pull back on the right stick, and don't work the pitch up and down, you'l do a figure 9 (it will hit the ground) also be sure you are in stunt mode! if you forget and try one in normal mode you probably will do a figure 9. I saw a guy do that a couple weeks ago, it was a nasty and expensive crash.
As usuall, i decided to push the limits just a bit today, so i was working on nose in hovering, starting to get the hang of that, so i decided to practice transitioning from nose-in to nose-out, did pretty good a few times but then i biffed a bit and the heli wandered too close to the recicle bin (i was practicing in my back yard) wham! crash number 3

oh well, fortunatly it just took out cheap wood blades and the feathering spindle. i'll stop by the local shop on the way home tomorrow and try again tomorrow eve. afer clearing out the yard of a few potential hazzards of course!
i guess the other advice is push the limit of comfort just a tiny bit every day, even if only for a few seconds. Fly a littel faster, a little farther, a little higher, turn a littel tighter, and then bring it back.
Maybe this weekend i'll try inverted hover (stopping at the top of a loop for a few seconds) crash report to follow...