"H.P." wrote in message
...
Then his CG moves forward and he's nose-heavy and outside the limits
envelope.

Granted, it depends on a few unknown factors. But I think it's unlikely
that the average bicycle replacing the rear seats in the average 172 would
result in the CG being too far forward.

With a 172 that already has a somewhat-forward CG and an especially light
bike, certainly the possibility exists. But it's a pretty remote
possibility, IMHO.

Pete