Del, how are you getting the cup ends off? Are you machining down through the welds? I want to do the same thing but I can't shorten them all that much, only .300", and I won't get all the weld area off. Plus I don't have a lathe....
I use longer 6 cyl pushrods,, grind the weld off,, if you blemish the insert,, doesn't matter,, trim exiting tube,, square end with valve stem grinder to nec LA length, install insert, plug weld compressed in a vise..