There are usually too many drawbacks to a rear mounted engine and not enough bonuses.

Here is a control line combat planes' wing converted to RC Flying Wing. As a C/L combat plane it was powered by a Fox .36....but for the RC conversion it is powered with a Super Tigre .15.
[link]http://youtu.be/6Uu8nqqhYxo[/link]

It took very little extra weight to do the conversion, all of the RC components are inside the wing.