The Mustang stunter is a cool plane, but somewhat dated and the kit builds extremely heavy. The small wing + excessive weight = undesirable. If you replace most all the kit wood, substitute wood for the plastic, core the wings, stretch the tail and stretch the stab/elev and it'll fly well.
We built two, the first came out extremely heavy and does basic maneuves (wingovers and loops) but anything more serious (overheads) isn't possible. The second has all the usual modifications and then some and it's never been finished. With a 35-40FP it's overpowered, and its really too heavy for a Fox 35.
It's a neat kit, but I've seen a bunch of them built that didn't amount to anything.