I cut it down flush with the lug afterwards of course. I used JB Weld, but if you might want to remove it in the future JB Weld might be a bit excessive. I've used it in the past for repairing an engine block, and it really doesn't give up without a fight. Brompton seat post shims are held in place by rubberised superglue like Gorilla Superglue so you could try that.
I have:
I cut it down flush with the lug afterwards of course. I used JB Weld, but if you might want to remove it in the future JB Weld might be a bit excessive. I've used it in the past for repairing an engine block, and it really doesn't give up without a fight. Brompton seat post shims are held in place by rubberised superglue like Gorilla Superglue so you could try that.