Instead, I might suggest mounting a 5000 BTU Frigidaire window unit in the back (slider) window of your Scamp
after you arrive at a campsite (you can't [or at least shouldn't!] travel with one of these in the back window.)
We have used a 5000 BTU window unit in both our 2014 Scamp13 and our 2017 Scamp16 Deluxe Layout A. It isn't as convenient as a top-mounted unit but, it is much quieter, cheaper, and it has cooled both trailers very well.
You can probably find several designs of mounting platforms on earlier forum posts.
It took a couple of design attempts but, I've now created a mount that protects the window and window track, supports much of the weight
down to the rear bumper of the trailer, and prevents rain and bugs from coming into the trailer.
I think that I've heard that the rear window of most/all Scamps since 1985 will open (both glass and screen) wide enough to accommodate the Frigidaire 5000 BTU unit (possibly other small units as well?). Still, you should open your glass and screen, measure the opening, and compare dimensions to whatever window AC you decide on.
After opening the window and screen, I pad the window track (bottom) and the top and side edges with either split pool noodles or rubber pipe insulating foam. I then put a 2-piece wooden frame (1/4" plywood + 1" x 2.5" to 3" pine) into the opening that pulls up tight against the foam/pool-noodles (with bolts and wing nuts) to seal out rain and/or bugs. (That frame also protects the side glass and trailer fiberglass against any damage that might otherwise happen while lifting the window AC into place.)
I then put a wooden platform over the wooden window frame and support the back edge down to the rear bumper of the Scamp
(with a PVC pipe) to support some of the weight
Most of the time, we don't need/want AC but when heat and humidity are too much for fans, we can still have a relatively quiet and cool/comfortable trailer.
I'm still trying to make the whole thing even easier to mount and prettier ... but it works!
Try not to be too critical but, the pix in the following Google Drive link may help you design your own mount