The Chipmunk flies great but I haven't been satisfied with the results of the OS LA 40. Seems like I may have a tank height issue so I've been a little afraid to push the limits with it. It goes rich around 6 o'clock on the outside loop of horizontal eights and it's rich during inverted flight. I have a 4oz. Sullivan slant clunk tank in it that is mounted against the bottom of the motor mount beams. My overflow tube may just be too high, so I'm going to add some fuel line to it and lower it. It exits on the side of the fuselage and it currently is about on the centerline of the tank. I'm going to make that change and fly it in an hour or so. I'm going to lean it out too, because I'd swear that I had some good engine runs earlier in the season. I want to make sure before I do the major surgery of changing the tank height.
I bought another Chipmunk over the summer that was already built and this one has an OS FP40 and a metal stunt tank in it and it runs great. I've done pretty much everything that I'm capable of doing and it does it all nicely. (inside, outside loops, horizintal eights, vertical eights. inverted flight and loops and eights from inverted flight, reverse wingovers and some other stuff that I can't think of at the moment) It's a pretty heavy plane but performs well despite it's weight.
When you build it pay attention to the weight. My kit was all heavy balsa that was the darker color with dark grain lines and very stiff. You may want to substitute lighter, more flexible balsa for planking the fuselage. I had one heck of a time bending the balsa over the top of the bulkheads on the fuselage. You could also use lighter balsa on the leading edge planking and the center planking on the wings.