[Hallicrafters] 6HF5 to 6GV5

[Jack Schrader]

I need to change the finals in my SR400 (6HF5) to an equivlent tube 6GC5. Only one problem is that the top cap on the 6HF5 is ~0.375" and the top cap on the 6GC5 is 0.250" and is necked up to 0.375 just before it gets to the top of the tube.

Question is, can I shim the smaller plate cap up with with some conductive metal, such as alum. foil, copper or lead flashing to the 0.375 dia. without affecting performance?

Thanks

Jack