Several questions that may help you answer yours.

What helmet camera are you using and what is its maximum resolution? There are a number of cams out there that are merely security cams which do not put out very good quality feeds to your camera. The best on the market right now seem to be based on the Sony EX-view CCD. That may be part of your size inconsistency.

Second is the jerkiness of the helmet cam. I did a couple of ski videos using a helmet cam, and it is really an art form to get smooth footage. You have to resist the urge to look down, sideways, etc, quickly, and essentially learn to move your body around without moving your head. Similar skills when you use a glide cam type unit.

I would agree on the music - but then again - i am an old fart.

One thing you might try is to add some different vantage point shots (frame mounted looking alongside the front wheel, backwards at the rider behind you, handlebar mount looking into your face) to get some variety in the footage.

Check out the footage on this site for some nice helmet cam bike footage: http://www.mtbikeoregon.com/video_dayride1_hi.htm

I am going to be working on some bike footage this summer, so keep me posted on your progress. It looks like a good bit of work anyway. Nice bike trails too!