I don't like too much expo for precision flight either. I tend to use 15-25 on all flight controls, and only use IMAC and 3D flight modes.

I setup the ailerons for the correct roll rate at the slowest point in the sequence and use expo to get the correct feel in slow rolls. I find that too much expo makes it much more difficult to really nail faster rolls, you either hit it exactly or are off by 10-15 degrees. With less expo you hve more chance of varying the end of the roll to nail it, yet still 'appear' to maintain the same roll rate.

For elevator I setup the throws for nice spins and snaps (some planes need another flight mode for snaps) and then set the expo to get the right feel. Too much expo and you find that you can't make those really small corrections needed to keep the line straight on a moderately windy day, like when it's a little bumpy.

For rudder, i tend to just use the max available, and ~ 20-25 expo. But then I fly mode 1 as well so YMMV. just be smooth on the stick and you've got the etra rudder if you need it... KE loop in unknowns anyone??

I always find that while mixing may fix some characteristic of the plane, it will (almost) always hurt you somewhere else. Take a downline mix that is 2-3% on the last click of throttle. I can feel this come in on a 45 deg downline when adjusting the speed as well. With too much mix I find that these 45 lines tend to wander more than without the mix.

Just my setup.... YMMV.