Hi there,
It doesn't seem to be constricting the base of his tail at all, that's good.
I saw your other thread, I didn't know it had been there for months.
Grace you tried gently scrubbing it with a tooth brush while hes in the
bath?
Sometimes adults just get patches that take forever to shed. As long as they aren't causing any harm it's generally nothing to worry about. However being at the base of the tail, you just want ri watch out for constriction and making sure he still has full movement of his limbs.
-Brandon