[AdamIsAdam]

In fact I did. Randall was very responsive and offered a suggestion. I'll paste his reply here. I asked my question here to see if others experienced anything similar since Randall didn't see my car for himself.
(In my opinion, I don't think the adhesive separated, at least it doesn't look that way to me.)

Without hands on the piece, one would think the bond separated at the
frame somewhere.

To answer your last question, even if the bonding separated the only
issue would be if you used a soft top, it might pull the frame up off
the windshield. This would happen to a plastic or glass windshield if
not securely bonded. Otherwise, it has no real affect on normal driving.
It shouldn't come out of the frame, if it's inside deep enough inside
it of course. And the only real issue the flex would have is if the rear
view mirror was mounted high up on the windshield like a conventional
car, which you'd see the movement more prevalent then.

Otherwise, quite a few install them with no adhesive... however, they
also have bottom brackets and center support rods.

Now, as a side note to help you out, this may "seem" odd, but it works
better than you think. To avoid drilling any holes in anything, make
yourself a center bracket out of steel. Stainless would be nice (only
because you can polish it). Then use 3M-VHB double sided tape on the
bottom and front of the bracket. Stick it on nice and tight. VHB allows
for initial placement and then cures after a day or so to be really
sticky. It also comes off with heat and doesn't damage paint. It would
be 10x better if you could screw it to the frame, and just use the 3M on
the bottom. It's not going anywhere. But if you have to glue both sides,
that's better than nothing.

That little addition will do a lot in flex reduction! You would be amazed.