Dbl belt systems and extra wheels on x plates

I like the idea of the dbl belts. Seems like a nice mix of speed and accuracy. In the videos and pictures I've seen the belts seem to fill up the slot. Don't the wheels need a good seat in grove? I'm guessing there is just enough left with the thin tape or glued I've read about? And what's the best way to clamp belts down?

I saw an extra set of x plate wheels offered as and upgrade are SMW3D. At first I was wondering how effective that would be without widening the plate. Now I'm thinking...

Dbl belt systems and extra wheels on x plates