Vic,

Let me first give you my qualifications: I know nothing. I have occasional bought of brilliance, but this is likely not one of them. But I think ...

One issue associated with a rear pusher is that the air over the top of the wing is moving faster than the air from underneath. Takes some of the efficiency out right there. The other, as Dan says, is that you have turbulent, spiraling air coming in from the front prop. One thing you might do is add an inch of pitch to the rear pusher to get some thrust back. Test it out and see how it goes.

Single motor operation is all nice and in-line, but there is still something to think about. If you have that beautiful scale 337 set up with smooth, scale like pitch response, be careful of front motor only operation. Your elevator will be much less responsive without the rear prop blowing over it.

Have fun!

Bedford