The Twister wing is only 490 squares, and a Stunt Fox 35 is a reasonably good match to that size plane, as long as it weighs less than about 44 Ounces; it is, after all, the engine that the Twister was designed to fly with. I've thought that the Noblers were as large a plane as the old Fox should be expected to handle, at approximately 525 squares (I know, TF's ads all said 550 squares, but that was incorrect). Of course, I did fly a Skylark during 1965/67 with a Fox 35, and it had 560 squares, with a weight of 48 Ounces.
My second Skylark, with an OS Max S 35, performed much better, even though it weighed 49 1/2 Ounces.