I recently purchased this bike mount for my Android G1. Out of the box, it didn't fit and, while holding on to my G1 fairly well, didn't withstand all my attempts to shake the phone from the cradle. So, it required a few modifications:
The bracket is not big enough to fit the stem. I had to extend it with some paracord and a couple zip ties:
The zip tie above keeps the paracord from slipping off the bracket (which is where the metal bar would normally lock into place). I used figure eight knots to tie the paracord to the bar.
After attaching the bracket, I reinforced the spring loaded phone clip with the metal clip from a pen. There's no gluing involved, I just slid the clip in under the pivot and used another small zip tie to hold it in place:
The final addition is a strip of velcro (it's green) that slides in between the display and the keyboard and attaches to itself behind the phone clip.
After my modifications, this system is quite rugged. I was not able to shake, jolt, or sling the phone free from the mount. I've also taken it on a couple of trips while commuting to work and it has held up beautifully.