I have steel one piece valve stems that allow me to install TPMS system on all the tires because the valve stems on the inner tire comes through the outer one. I got the valve stems from always shiny wheels (at least I think that is the name) on line and I sell the TPMS system. I tried valve stem extensions for a while but they wouldn't give correct readings and had a long one break. This system works fine and both tires are independent of each other.
Don
Don