Hi Mark,
Magnum and OS max are very similar. Magnum has a ball bearings. My Magnum is pretty old (3 years of running every sunday, in winter too). It turns MA 8x4 11500 rpm. Os max.15la is new and turns 13800 rpm with APC 8x4. I hope, it will be better than Magnum. I will try it on sunday, if weather will be good.
OS 25LA can be good way, to get a power enough, but I am afraid about wing loading. Now it is about 32g/dm2 and landings are really gently.
On the picture is second prototype of my .15 powered 3d planes.
I love this small things.

Lada