Cooke Speed Panchros (TLS) with Extender

Hey all, I'm thinking about renting a set of TLS panchros to pair with a mini LF. I know that anything wider than the 40mm won't cover the whole sensor. I'm wondering if anyone has any experience using extenders with these lenses?

My plan would be to use the extender (ideally a 1.4x) on the 18 and 25, making them effectively 25 and 35. Then I'd use everything from the 40 on up without the extender.

I know not all extenders are compatible with all lenses. Sometimes if the glass protrudes too far from the mount, it makes it impossible to attach the extender. Has anyone used extenders with these lenses and if so, which ones?