John, I talked to Scott at Selden US today and he is going to sent me a new gas spring one size stronger like you had put on your C309. He said they should last 10-15 years without failure. He thinks the ones on the early C309's may be undersized for the weight of the boom. Mine is #20 and yours was about the same. Thanks for the info as it gave him a clue as to what was going on. Hope your are having a great sailing season on your new C355. Bob