99 % of HD mini cameras suffer from rolling shutter which will bend the prop
I think this topic came up here recently.
The only real solution I have found is a camera which has a manual shutter speed control. The G10 is the first camcorder I've had which has that, and 1/120 or slower gets rid of the prop. That Alps video was done at 1/120, and at 2400rpm it works just right. At 2300 or 2500 I need to use a slightly slower shutter speed, oddly enough.
Neutral density filters can help the cheap cameras to slow down their auto shutter and reduce prop effects but I have never been wholly successful with that.
Suction mounts are not good on perspex
Have you seen that link I posted to my suction mount pics? They work superbly on the TB20 windows. I have added a security "rope" however, so if the suckers gave way, the whole thing is not going to fall down onto something important.
I did one experiment which was a 2hr flight, resulting in an obviously mostly utterly boring video
here which was filmed totally hands-off, using the suction mount. The image quality on that one is not good because I transcoded it (using Handbrake) using a 1megabit/sec average bitrate which is about 5x too low for Vimeo. (The soundtrack on that one is also badly shifted, over most of it).
For filming out of a C150 which obviously won't have an autopilot, I don't think a handheld camera is going to be easy. So it's a choice between brief handheld clips, and mounting a camera somewhere properly.