I seem to be having increasing trouble keeping split shot in place on my tippet.

I usually use 5x fluorocarbon tippet and tin shot. After half hour or so of fishing, my shot slides down to the fly. I'll open up the shot and reclamp it in place, but it quickly slides back down again.

It seems like this problem is particularly troublesome with fluorocarbon. My understanding is that fluorocarbon is harder than mono and will cut a groove in the shot which is the root of the problem.

So I'm wondering if anyone has any tricks for securing tin shot on fluorocarbon tippet?