I suppose this is a bit of a bad moment to tell you that, but that landing gear is too far back. With the new Orbiter's ground contact model, the elevons won't have enough torque to push the nose of the craft up.
The landing gear should be close to the CG, but behind it. That'll ensure the plane doesn't tip back on its own and the the air control surfaces have enough force to turn it over. You'll have to resort to moving the CG back and the touchdown points forward.
The other very ugly cheap trick you can do is to extend the length of the front landing gear, so when the craft is on the ground, it sits at about 5° nose up attitude, so as it rolls down the runway, it already has an AOA of about 5°. As the plane picks up speed, the wings start to produce lift and the effective weight of the plane decreases (that is, the force required to turn it).
The reason this trick is very ugly is because the engines will also face down - unless you vector the exhaust - and dig a trenches into the runway. It also makes for very difficult landings, as you're landing with a 5° nose up attitude, so I'd recommend you avoid that.
Pretty much all DG class ships suffer from that.
Notice how far forward the landing gear on the X-48 are. At least a third of the length of the aircraft is behind the landing gear and that way the control surfaces have a long enough lever to produce the required torque.
On the F-22, you can see the landing gear is about 3/4 of the length back, however, there's still considerable distance between the elevator and the landing gear. The elevator - the flying tail - is also huge and produces a lot of force, so the F-22 can afford to have its landing gear further back.
But in the case of the XR3, we're not exactly talking about a maneuverable fighter jet... It's tough to see where the landing gear is exactly, but I'd say 1/5 to 1/6 of the spacecraft's total length from the back...
Some more images: