Making a Pentax 6x7 extension tube

..I'd like a tube thinner than the shortest tube available. I think it can be done by re-purposing a teleplus converter by removing the two mounts and the screwing them together minus the tube and optical block. It may only be 3mm shorter than the no 1 tube - but it would help a lot. Has anyone tried this? ps I don't want to go the cu lens route for closer focusing. This is not a Hasselblad posting.

Try it and see.

What are you trying to do that would require something like that?