Can you replace a triplock 24-7030 tube with a correct twinlock 24-7000 in a 5513?

[g-boac]

Got into a conversation with another customer at my local AD. He said it's not possible to retrofit a vintage sub (specifically, the 5513/5512s that originally came with twinlock crowns) back to a twinlock crown, because you have to bore out a larger diameter hole and tap a new thread into the case when replacing the tube. That makes no sense to me - on a couple of different levels (both manufacturing, and service) - but he was insistent.

I was under the impression that in order to switch crowns, you needed to also switch tubes - but that the process was as reversible as having your watchmaker screw one out and screw the new one in. And that the real trick at this point lies in sourcing the correct parts.

Can anyone shed light?

thanks!