I've flown the Cherokee with an OS .55AX and found it a really nice plane, and that engine is a perfect match for it. I'd easily recommend it as a second plane. Fly it with the controls tamed down for a while, then increase them with experience and you'll have a great basic aerobatics trainer. I've see it with the .46 AX and think its faster with the .46 but has much better vertical with the .55. Knowing almost every pilot who flies will want to do aerobatics with it, I don't see any reason not to put the.55 on - it'll perform them much better.

Hogflyer