I had nothing but problems over the years with extensions.
I know you can get them to work...but I found they may not be worth the trouble
The flexible ones that Thor put on leaked
I replaced with some rigid ones I bought from ebay that were better, but needed rubber stabilizers. I still had some problems with the internal stem getting bent
I never tried them, but I think the best solution is likely these
Dually Valves - Inner Dually Stems
and they would be put on by the tire shop.
I finally ditched my wheel simulators. yeah, they were pretty....but they were the root of all the work and problems. Without them, I can get my hand in there to install or remove the TPMS sensors (or dust caps)....and now that I can get the dust cap off, airing up is no problem with the right inflator. No more extensions to leak or interfere with my TPMS sensors....and no more worries!