I highly recommend you look at the Northeast Aerodynamics Aquila. It's by far the most airplane you can put behind a 120AX or similar. Very light for it's size, it presents better than what you typically bolt a 120. It's only slightly smaller than a Focus II. It will accomodate a 140 size engine if you want to, but it really doesn't need it. Needs very little mix, and locks a line quite qell. It's also a very effortless airplane in slow and point rolls, having a very light work load with the rudder. Snaps very well, stops on a dime and has a very positicve spin entry and recovery.