the Irvine 36 heli has 2000 RPM over the standard and is a great engine, the fins will help with cooling in this high temp stuff.
Correx will be too heavy. go Dust style with hardly any ribs, but 1/8th ply ones when they do. i couldnt believe how light my rebuilt one was even tho it had 1/8th and 1/4 ply all over. dont do a full ply fuz tho