Hi Jae
You have a few options that have read about here and tried.
1)metal Stud finder - personally used successfully to mount a tv hold on the wall of a 3950
2)call heartland to get schematic of the wall in question - Tried without as much luck, hard to read and they sent a generic diagram of the wrong wall.
3) check outside of trailer in the morning for dew lines after a cool evening, you will see the fame outline, this works and I confirmed with the stud finder too.
That being said, I am not sure how much weight you want pulling on your walls, our tv was small and light and we never travelled with it on the wall. A motorcycle tied to it might be a little heavy?
I am sure others will chime in with other creative methods too.