I have the same ARF kit, and I am planning to put a modern Fox .15 on it. It is also iron piston steel sleeve, but it will turn an 8-4 prop at almost 15,000 revs. Not sure it it will hover with that old Enya. What nitro fuel did you use? Some of those older .15's needed high nitro fuel, such as Cox racing or Missle Mist.

Thinking of reinforcing the plastic fuse on this model. Not sure how, but thinking of gluing some 3/16" square balsa, in four courners and top, to the rear former and gluing the stabilizer to that. Or maybe it will hold up fine without?