Hi Roger, my NC33 is a 1989 model, I am not familiar with any locking mechanism on the gooseneck, but that would seem sensible. I can’t get to my boat at the moment because the yard in Glasgow is very closed. I just wanted to check that the boom was supposed to slide up and down before I drill out the rivet holding it in one position. I am sure that the rivet was put in for reason despite there being a small downhaul purchase on the gooseneck to tighten the luff (although in effective with the rivet in place). Its not really a big problem but I am 6ft tall and when not sailing it is very much in the way when relaxing on the aft deck or using the aft deck steering position. I will take a picture of it when I get back on board, and post up on the forum. Thanks again for your post.