I don't have specific experience with bigger motors, so this is slightly theoretical:

The two things that set your maximum RPM are the fact that you want to maintain regulation throughout the whole flight (as the available voltage from the battery sags), and the fact that you don't want to burn up your controller or motor.

For regulation, the recommendation that you'll see over and over again is to allow for a 20 to 25% drop.  You're starting out with 14.8V and a Kv of 900, which works out to a theoretical full-battery, flat-out RPM of 13320.  Drop that by 25%, and you get 9990 RPM.  Choose an RPM over that, and toward the end of the flight you'll notice the motor sagging in the up-lines, and anywhere else you're asking for lots of power.

For current draw, well, I'm not sure because I don't fly that sized motor -- but I took a quick look at similarly sized motors on the Hobby-Lobby website, and their recommended props seem to be in line with what you're choosing.  Particularly since you're always going to be throttled down a bit, I suspect that you're OK from a current draw standpoint with that prop.

If you can, check the current draw from the battery on the ground -- that's the most current you'll ever draw, and as long as it's less than 50A, you (and your ICE 50) will be happy.

John,
I agree with Andrew on the RPM setting as a good place to start. I would not be surprized if you eventually end up slightly under 9000 with that plane. What timer will you be using?
William

John

A smoothie with that prop on 63 ft lines will turn a 5.25 sec lap at 8400 rpm.

bob branch