Repairing water-damaged inside sidewall

[p00ches]

I have extensive water damage under both main slide-out windows. I caulked outside both windows, and the gap between the sidewall and the top of the window awning. I cut away the wallpaper and swolen 1/8 inch luan, revealing aluminum framing with intact foam insulation in between. Letting it dry out now. Hopefully I stopped the leak! I'll know soon enough, it's raining like crazy now.

Having a hard time finding 1/8" luan, but found 1/8" wallboard at Home Depot. (1) What would be the best 1/8" stock to use under new wallpaper?
(2) What adhesive should I use to install the new 1/8" board. Any other suggestions? Thanks in advance, Doug 2003 JourneyDL 36GD

[skigramp]

I had some water damage under my bedroom slide .... I was able to find some "Masonite" paneling which nearly matched the existing wall ... I used some edging and installed a piece to cover the damage ...

I mention this because have you considered removing more of the wall and repaneling the whole region with new?