Yes, to clarify you can't really cold-form acrylic
unless the curve is very slight and didn't ever mean to suggest you should. It's just too brittle and will break. You really only want to use polycarbonate for this sort of thing.
If thermoforming, making the curve doesn't matter, both types will bend no problem so at the point its a material cost vs material performance issue.
For what it's worth, I have experience machining, thermoforming, line-bending, and glueing both acrylic and polycarbonate, as well as a bunch other plastics, with some additional experience specifically break-forming and rolling polycarbonate sheet.
At one point I was working on an architectural glazing application to basically make a sort of corrugated vacuum-insulated panel with less weight and greater depth
than a typical one inch glazing panel using less material.
Unlike acrylic, poly is both more flexible and more pliable. In the case of cold-forming, at minimum bending radius per thickness it can be permanently deformed below without appreciable degradation of the optical qualities.
Generally, material thickness continuity and surface gloss determine visual appearance. When you exceed the material limit you will see sort of striated opacity along the bend axis, like if you form a cold ninety. The thing, is you see this same thing when you line bend anyway.
Besides being quicker, faster, cheeper where practical, cold-forming is best because it limits the risk to the material's surface and thickness. I have dealt with some guys who do medical
stuff or display cases for the MOMA and the MET and even they will tell you perfect doesn't really exist, so anything you can do to minimize altering the material will be of benefit.
In your case, if you didn't feel comfortable just applying it to the cabin
top with screws or if you wanted to go screw-less, talk to your sign guy about having him try to roll it for you.
Screw-less is worth looking into in my opinion ands might be worth some sort of forming operation. If you can get pretty close with your formed workpiece you should be able to get the rest of the way with the VHB and some propped up 2 x 4's, but at the end of the day screws are probably easier.
Just guessing at the width most shops should have the capacity to handle the width. They might baulk at the thickness you want to use if they haven't rolled poly before but remind them it's just plastic and not metal.
Like I said, best to play around a bit and make a mistake or two while you figure it out. As a general rule
, the builder
before you always took the easy way out when he built whatever you are trying to reproduce and so should you.