Apologies, I read your reply on my phone and missed the questions at the bottom of your last post.
Yes, you do need to roughen the foam up a bit, but not too much, as you don't want to the glue to go into the "valleys", thus reducing efficacy. Panels have not been tested to failure, I simply do not have the proper tools or equipment to do it. I could drive a truck over it or something along those lines, but I do not have any way to scale or measure said testing procedure.
As far as glue goes, any industrial or commercial grade spray contact cement will work. Stay away from Home Depot spray glue and the like. You will need a spray gun with a large tip (HVLP works well) and a compressor to push it. Finally, you will either need to wait for good weather and spray outside or make some kind of "paint booth" type of structure, as it does make a bit of a mess when spraying a fair amount of glue on a large panel. Next time I am at the shop, I will try to look and see what glue was used. IIRC, it was something like this:
https://www.helmitinadhesives.com/products/cementssolvents.html
Any autobody or automotive trim supplier should be able to get it for your if they do not have it in stock. I checked for distributors in NM and the corporate site does not list any but there are several in the states around you.
DAP and 3M both make similar products, but I have had less than stellar experiences with those companies (caulking and VHB tape, respectively, not contact cement) YMMV