[rames14]

First, a couple of things. Montana has gone from steel to aluminum and back to steel joists. I believe they are still steel. Part of the reason for changes are weight, condensation and subsequently mold issues. The metal does not contact the roof. Their is plywood or particle board sheeting attached over the joists. You should be able to find the joists with a stud finder, but also looking at where the AC units are attached. They use a common spacing, so find two and you can find the rest. The solar panels work best if they have airflow under them. So, they use steel stand-off brackets to attach to the panel and roof. Make sure to seal over your bolts. If you have roof mounted satellite, do not run your cable under the panels. Best of luck.