I've always thought that rocket gliders were the biggest challenges.  There are really very few.  Most of the favorites (Crusader Swing-Wing, Scissor Wing Transport, Citation Bomarc, Trans-Wing, Deltie, Soaring Eagle, Mach-10, Mini-Dactyl,  SST Shuttle, Swift, Nighthawk, etc,) are boost gliders  which use a pop-pod which is ejected.  The most simple of these favorites like the X-24 Bug, etc still eject the engine  casing.  The only true Rocket Gliders I can think of are the  Estes Tomcat, Edmonds ECEE, and some competition models.  Competition models generally use nose mounted engines with  burn string activation for either sliding wings and/or control surface activation.  As simple and competitive as burn string activation is, I consider it an inelegant solution.
The Falcon eXtending Tail Rocket Glider uses the ejection charge to extend move the CG backwards and also activate the aileron.  A moving control surface on the tail isn't really necessary, but I'm concerned about getting a straight boost.

My original design criteria:
1) True Rocket Glider.
2) 15 degrees minimum wing dihedral.
3) Scalable to 13 mm engines for A / 1/2A RC competition.
4) Constructed from readily available parts
5) Quick prep - No burn string.  "Plug and Play"

I have some initial sketches for a Generation II XTRG which will be called the "Raptor."