The +15 degrees is way too much pitch for that motor and would bog it down a lot. I have my pitches at -3 to +11 in normal and -11 to +11 in idle up mode. I dont' know why you are getting a different pitch reading in idle up and normal. With your settings you should get the same top pitch in idle up and normal mode. Does it look like you have equal distance on the main shaft under the head to swashplate and from the swashplate to the retaining collar in idle up at half stick? Does your servos start making different noises than normal at the top and bottom limits? I have my swash mixes at 60%. I tried what arrownaughtic was talking about with the pitch curve, but by the time I got +11 degrees the pitch curve was at 52ish. So I had to use travel adjustments to get +/- 11 degrees and keep the swashplate level at bottom and top stick.

Nick