[garyinla]

For example, I borrowed a 10m for a gig. The thing was so unbalanced, the mouthpiece kept hitting me in the mouth. It was clunky and tubby sounding.

This is a well known condition caused by the placement of the neck strap lug in a different location, by Conn, on purpose. Ive read they did this because they put out a sax stand (made to play while standing up) and the original neck strap lug location was interfering with the stand. I have a 10m and my repair tech removed and replaced the neck strap lug, to the proper position of balance. This is a well known fix. Some techs put on a 2nd neck strap lug instead.