I also notched mine where they screw on, Mine have been there a year b ark still on, and Mine are flat.
Joe, the bark was still on my branches, too. It appeared totally fine. But, after noticing all the drama at roosting time for awhile I finally went in there and ran my hand along the branch and that was when I realized it was worn smooth...and slick.
I should also note that the dip I spoke of was very minimal. The branches appeared nicely flat and straight to me, too (or else I wouldn't have used them). But, they sure noticed it and, when the roosts became slick they couldn't roost in that spot.