Murdoc,
The GMS .47 is a very powerful engine for its displacement. My son has one on his Hanger 9 .46 size Harrier and with a 12X4 APC prop it will pull it vertical till out of site. Hovering with it is no problem at all. He also has an OS .46 AX and an OS .46 FX and the GMS will out pull both of those engines easily on the same size props. Just be aware that the engine does require a proper break in period and it can be cranky till broken in fully. It isn't as user friendly right out of the box the way OS engines can be but once broken in it will out run and out last the OS engines in its size class.