I think your comments are valid, this engine is also has industrial engine roots like G62 in likes to rev high. Tested engine is nearly brand new, never been in the air, the second one I got has around 30 flights on it according to previous owner and both of them has a lot of compression. I have installed the second engine after work. I will test and later swap the ignition and carburetor to isolate the problem. I might try 22x8 to get a bit more rev.