[Frank Lee]

Well, I think the flex point has to be right there where it was, or darn close to it, in order to best do it's job.

There are a few things to keep in mind:

That the engine rocks- at times more than you would think- and the exhaust pipe has to be able to handle that movement.

That the pipe needs to be isolated from the chassis via rubber hangars or unwanted vibes and noise get in.

There might be a "growth" component too, from when that length of pipe goes from cold to hot, that makes rigid mount bad. But I haven't ever really looked into that. And I know you aren't talking about rigid pipe hangars.