I would say you are safe to up around 200F for limited amounts of time. Skis are pressed with much higher temps than that, so you will be safe.
The temp you hotbox at also depends on the hardness of the wax.
If you are interested in absolute control of your temps to within a degree and having a prostyle set-up for doing so, I build and sell a hotbox for backshop use, and we are developing a pro-sumer/consumer friendly version. I would pass on a link to my site, but don't want to spam. You can search my name on TGR and visit via my sig link to learn more.