I have never kept track of how many times I assemble and disassemble a lock while building one. I suspect it goes into the hundreds. If the spring works satisfactorily , you could mark the tumbler nose right where the spring hook lies at rest and file the length back to the line. By getting the tumbler nose out of the hook, the full cock draw will lighten up, even if it still bears on the inside of the hook, it will be less. I like to build locks in pairs or sets of three. that way when I get into a jam on one, my awareness heightens and the problem can be approached differently on the others. Another secret to lock making is to build the lock (s) a year or so before you start the gun. That takes ALL of the pressure off of delaying the whole build and the problem can be solved more easily. Lock making is not easy, but I really enjoy building them.