-
Weird, both my alu seatposts have got quite big marks from the two bolts on the SQR block. Definitely not something I'd want with a carbon post...
Although my list of stuff doesn't sound like much, I'm carrying the same amount of stuff currently in a Carradice Stockport bag (also 16L) on my Brompton and that's pretty much full. Again, not compressed, but it fills it.
TurtleRecall-
The bolts shouldn't touch the post should they? The two bands just tighten around the post and the bolts should be short enough so they stay shielded by the plastic of the unit itself.
My alternative to the carradice when I've got less to carry is a full length top tube bag. I managed to pick up a home made forum option which works well if not packed too full (otherwise it brushes my legs):
https://www.lfgss.com/comments/13332264/
Scrabble
I've had an sqr on a carbon post for years. No issues to report.
In my head, you clamp it pretty tight in the seat tube, so clamping in the same way with the sqr should make little difference. To date my findings have supported my hypothesis.