I'm interested in using the proclip bracket (fits across an AC vent).
I got the pro-clip mount and put a double-T mount on it. To that I attached the moto cradle. The angle is pretty much perfect for viewing at the wheel. The back of the cradle has a protruding USB socket. Using that with a straight USB plug causes the cable to come a bit too close to the radio behind it. So I got a right-angle micro-to-mini USB adapter (via ebay) and connected an old mini-usb charger left over from my XV6800. The whole setup works great. No need for the ball mount at all.
I tried a vent mount and was NOT pleased with it. The clips don't grab the vanes of the vent securely enough to make decent use of the phone. Touchscreens are tricky to operate and the way the mount shifted made it problematic to use the screen. Missed or doubled taps were a big problem. If you're going to pick up the phone to use it then, maybe. But if you expect to use the phone while it's in the mount I would not recommend one attached to a vent.
The downside is now my 2yo son wants to see picture slideshows on it. "See family at the beach?" calls from the back seat...
Where did you mount it? I think for my car there are 2 choices (side of AC vents and on the console at the bottom). Do you have a link for the mount you bought so I can see the "T" you are talking about. So, you just took the cradle out of the moto mount and that went straight on that "T"?
thanks