Hi Simon, I think I’ve only seen the two sizes? It’s definitely not a 'long shaft' (ie 3/4" worth of thread) body. These pots are long enough for the cavity as is, but there’s not a lot of thread left over (on the thickest one at least), so adding an extra 1mm of timber inside the cavity may be pushing it.

They look like they have a locating pin that I didn’t see when I test fit though, I may get away with it. I’ll have another squiz tomorrow.