On my old NP booms the rubbers on the clamp went hard / soft / brittle doughy and fell off. I stuck some 3mm rubber square in there and carried on.
I saw a Chinook Pro 1 alloy boom which had the same problem.
is this common with the types of rubber used on those boom clamps. We're they neglected, sun?
Im thinking of getting a Chinook Pro 1 Alloy but I'm scared that rubber will go, it looks like it's moulded in. Ugly fix.

Nice image
From my experience blue rubber on some neil pryde boom shims only lasted 12 months
Replacement part is hard to find and pricey

Yeah Manu's got the right idea.
It's a trivial problem with an easy fix. You can just glue (contact cement) some inner tube to the gate or if you find a big enough tube you can just slip it over the gate. Come to think of it some of that vinyl tape that sticks to itself might do the job.

My ancient Windsurfing Hawaii boom clamp rubber is as good as new, same for my Epic boom. Could contact cement in a couple of layers of truck tire inner tube rubber, I did that on the Epic boom, 1 layer, because the original rubber was a little on the hard side and boom clamp slipped occasionally with moderate clamp pressure. The inner tube rubber worked perfect, no more slipping with moderate clamp pressure. I avoid high clamp pressure with 100% carbon masts, heard you can crack them that way.

Manuel7 said..
It's possible you can crack especially older sdm's. The clamp handle should prevent anyone from applying too much pressure, plus the head has enough give to release tension as well.

I've broken 2 rsx masts full carbon on unpacked techno boom clamps

You mean head rotation. Its stiffer than when it's loose for sure! But one can adjust the height normally, no problem.