Yes the mount is pretty solid. As far as a weight limit the stated limit was several lbs. Any compact camcorder should be fine. I would imagine that the mounting on the camcorder would give out before this mount did. The plastic area around the mounting hole on your camera is going to be the weakest link. I've broken a camcorder before when it fell of the tripod. The plastic surrounding the screw basicly shattered as I panned the camera up to catch a bird. Little bits of plastic fell inside the camera rendering it useless. Canon sent me a new one after months of hassle.

If you have a Hi-8 I would recommend you get some T6 alluminum and machine a metal base for the camera to rest on. The cheapest way of doing this would be to get a small 1/8" from a machine shop, or if you can't find one, try an RC car shop. They often sell gas RC chassis that are T6 alluminum. In any case this will help re-inforce your camera if your doing any offroad stuff.

I also use a velcro strap as a safety backup to prevent the camera from falling off the bike should the mount or camera mount fail.

Sony makes a lipstick CCD specially for this kind of situation that can mount to a helmet and feed video via composite to a camcorder in a backpack. They are like $199 and are the best solution if you are going to get rough.