I vote Jett FIRE 50. After owning two DD's and following their threads for years, I don't think the small diameter props will give you much speed advantage. The Dust is not clean enough to avoid the thrust = drag speed barrier IMO.

Other things to consider:
A throttle is nice. I can not imagine not being able to throttle back to prepare for launch. Not much to hold onto.
Serious mods are needed to mount a rear intake engine. It can be done though.