Tractor or Car iPhone Mount

I have the DLO HybridShell for iPhone 3G, 3G S case for my iPhone. All the car mounts I found for the iPhone were custom fit for a iPhone without a case, so I had to build a custom holder, and this is what I came up with.
I have used this for a month or so driving tractor and my iPhone never once jumped out of it. It is open on the bottom so the charger can be plugged in. I just mounted it with double sided tape, and it worked fine.