RE: 31cc Atom Motor
I just looked through the pdf manual and in the parts breakdown it looks like a Ryobi.
I have a few of them. There are a lot of modifications you can do to them . At a minimum I would put in some Bowman rings, a bit larger carb and just that will make it a good running engine. From there you can lighten the flywheel, trim the backplate, machine the intake and exhaust and put EI on it. I have one running on EI , Bowman ring, 11.1 carb,trimmed backplate , better muffler and some machining on the intake and exhaust and it is a good powerful engine.
The standard conversion work will result in a good engine for a warbird or other scale plane.
There is a thread here about converting them titled "another ryobi conversion thread" I believe.
As far as the engine mounts you can make and bolt a plate or ring over the plastic backplate using the existing screws and then mount the standoffs.on the plate/ring.