Don't forget that no matter where you moun it, you need to be able to reach it with your left hand to press the button to take the picture. And this assumes that you have somehing worth taking a picture of. And a place to take it from.
Remember that the camera only sees a limited amount of what's in front of you, and that limited frame of reference will drastically change how the picture appears.
This is the best of about 10 pictures I took this way. The rest were also taken in curves, but because of the camera, it appears to be flat ground. And even though I was following fairly closely it appears that the riders in front of me are far away.
So would I bother with this again? No, it's more work then it's worth to get the camera on, then take the pictures. Because the pictures aren't particularly good.
By way of contrast, I kept my camera in the tank bag the rest of the time. I turned it on in there, grabbed it left handed, pulled up beside (2 lanes each direction with no cars anywhere near) Malice and snapped a bunch of pics, then stuck it back in the tank bag zipped it up, and hoped like hell that the turned out well. Of 7 pics of two people this one turned out the best.
So, freehand works better, though it's amazingly more dangerous. Which to me means that the best option is to get a pillion and have him/her taking the pictures.
Of course I'm generalizing from a single example here, but everyone does that. At least I do.
[url=http://sirac-sev.blogspot.com/][img]http://i12.photobucket.com/albums/a227/Sevulturus/sig.jpg[/img][/url]