I'v always reach a kind of speed limit with my miniquads above 70-80km/h. Probably because of the frame beeing so tilted that it create too much drag.
William from Schrediquette project made some wind tunnel test using tilted motors, and results are promising.
I've made some 3D printed mounts for the Pocket Rocket, you can download them on Thingiverse
This also help to see other thing than the grass when you're going fast.
First test yesterday, and I confirm, this is really promising.
Also, those 6x4.5 props are strong drug.