Front derailleur rotates on frame

[OakLeaf]

okay, now that there's light...

First thing I tried was the L limit screw, and that fixed it. (Yes, I did try that back in December and that's definitely not what it was then.)

As I said before, the cable is and was plenty slack when shifted to the low position.

But that begs the question of how the screw spontaneously tightened itself. If anything, you'd think it would back out, and I really wouldn't expect that screw to move at all.

Also, just for grins and never mind why I didn't do this months ago, I put a torque wrench on the clamp. (A good CDI click-type torque wrench, same one we use to put the valve covers on the motorcycles, not a cheap beam wrench.) I set it to 50 in-lb (well within both Shimano's spec for the clamp and Cannondale's spec for the seatpost clamp), and it turned a full turn without clicking, at which point I quit tightening it any further.

Any input on (1) how the L screw could have tightened itself or (2) what the proper torque on the derailleur clamp should be?

[aicabsolut]

There is probably a spec/manual page for Cannondale somewhere. At least all the warning stickers on my Specialized says to check the web manuals for torque specifications.