Hi Paulie,
I don't like the Diatech at all.
It has two functions: tension the headset and keep the fork in place when you fold the bike. I never managed to set it up to do both. Every time I folded the bike, it came a little bit loose and had to be adjusted again when un-folding the bike.
Now that the Quest doesn't have front suspension, there is no reason not to use a regular headset and a locking headset like this one:
http://problemsolversbike.com/products/locking_headset_spacers
Hope someday Cruzbike will make that change.
What I did to my Quest and improved setting up the Diatech was to pretend it was a regular headset. To do that I inserted a star nut in the fork steerer tube, and welded (JB Weld epoxy) a threaded rod to a headset screw (had a long nut between the two) to reach the star nut from the top of the Quest steerer extension tube.
Now whenever I need to fold it, I release this long screw, release the pivot clamp a bit, tight the Diatech enough to keep the fork in place and fold it.
When I have to unfold it, I insert the steerer extension and pivot clamp back, use the long headset screw to hold everything in place, loose the Diatech and now use the headset screw to get the proper tension in the headset. Then I tight the pivot clamp, and then the Diatech just a little bit for the final set up.
Works great for me. Of course if you manage to set it up, and don't fold/un-fold frequently, you don't need the headset screw.