I use Loctite Power Grab in a big S pattern as well as on the outside border 2" in from the edges of the sheetrock and well as a few screws where the vertical seam is.
This is a method I learned from ONYX solid surface tub surrounds Joe. Apply the adhesive in 2" circles about 6" apart and around edges. This material uses 100% silicone but works with other adhesives. It will stick a 100 lb. sheet to the ceiling with just enough props to insure full contact. The instructions say to pull it back for a few seconds after the first installation, but the suction cup effect is like trying to pull an octopus off a fiberglass boat. I also did Hardie Plank panels with the pattern too. Same effect.
I was not putting down mobile homes, I have worked in some really nice ones, like you are trying to make yours. The last one I painted, I just removed all the trim that covered the wall paper seams, skimmed them all out, sanded, cleaned, primed and painted. It would save you a lot of work re dry walling, I would think.
Chrisn, when you did this, did you remove any of the vinyl coated paper, either by cutting or by sanding off the paper?