Porta-bote Mounting -need help

[Jim-n-Kathy]

Hello folks,
Well as usual; due to my busy work life I only seem to come visit ya'll when I am in need of information. I hope the old time clock changes all that soon...
Anyway, after years of research we finally acquired a Porta-bote. Now instead of camping at the edge of a pristine and glistening lake and watching nearly every other RV'er on the water-we will be leaving land too. Only prob; [and here's the question]; I am ready to install the mounting brackets to the Monty's exterior and even though I am a pretty good construction dude-I am wondering how I can pinpoint the wall studs accurately the first time. The material is took thick for a stud finder to read correctly. And I am not that enthusiastic about removing interior panels. So, got any ideas.
My wife knows that when doing drywall I ocassionally miss a stud, but if I pulled that trial and error on the Monty I might just as well plan on tent camping!
Thanks,
Jim and Kathy in Folsom, CA