when we purchased our home we replaced the hot water baseboard heat covers. now that the heat in on–the is an awful racket in my bedroom when the heat comes on. i know we crimped some of the “fins” when we were replacing the covers.
It can take some patience, but straightening the fins can provide some relief. The fins rub against each other and their carriers at times. Efforts to reduce contact with obstacles that the fins catch on is worth the time. The plastic carriers can be moved slightly to keep a fin from being next to the end of the carrier.
Baseboard pipe movement can be reduced by using a quality stand-off pipe clamp at the middle of the baseboard. You might have to remove a few fins, but it will not noticeably degrade the heat output.
Check that the riser tubes do not touch the wood as they pass through the floor, you might have to cut the floor 1/4-inch away from the outside of the pipe so the pipe can expand without binding and noise. The hole can be closed to passage by some silicone caulk.
Add lengths of baseboard to the existing baseboard; they do come in 2-foot lengths and up. This requires opening the system to add in the length. To know if there is enough baseboard, go to the design lessons at http://www.hydronic.net
A ot water heating expert may know other ways to surround you with baseboard and have the room controlled by a non-electric zone valve.