Picture Tube Swap?

[leadlike]

I think the very first post I ever made to the forum was about this issue, and now I think I may have a means to solve it:

I have an RCA 21" set that uses a 21amp4a crt. That tube is now REALLY shot, after a rejuvenation that kept it chugging along for a bit, it must now run on a brightener to deliver any image at all. I have a 21CBP4 sitting in the shop now, and it tests like new. Is it possible to swap these out? The only difference between the two crts lies in their methods of focus-the set uses magnetic focus, while the 21CBP4 uses electrostatic focus.

I was told that one could run a jumper from the G2 pin to the focus pin and it should work in place of the 21amp4a. If that is true, shouldn't I remove the magnetic focus assembly as well, and I shouldn't need the ion trap on the new tube, either, right?

I just happened to have this set on the bench right now for a vertical problem, so I figured I'd replace the crt (if this is really possible) while I was at it.