Rates are not required, 100% on the servo movement and mechanically adjust the elevator movement for reliable spin and snap. That is all you need. How you can fly the pattern and remember to switch elevator, aileron, rudder rates for each segment I do not know. You will have enough to do just getting the thing in the right place and height for the next call. Any loop will need constant modulation of elevator and engine to maintain the shape, there will not be any 'rate setting' that allows a round loop. As you suggest, the hardest thing an aerobatics is to consitently 'fly the line'. That is the first thing to practise, any other pattern shape is just a 'wrinkle' on the line. The next thing to practise is constant height pull-outs. Leave the tricky stuff until the basics are down, they won't be so tricky after that...
Evan, WB #12.