The way I framed out the unit this cowling slides over the AC very tightly under the angle up against a neoprene gasket. Without the cowling the camper has set through a number of storms, no leaks so this is mostly to keep dirt, dust, leaves etc out of the AC. Also should protect the fins and provide even more water intrusion protection during a tow.
I pondered for some time how I might affix it for travel but after installing it I ha e to think it's fine with nothing more than a friction fit. It's snug and takes a few pops to get it on all the way. Thought?
It's 8" deep.
This should also be very helpful in the winter when we don't need the AC.