Unfortunately Albuquerque is in the unenviable position of being the car theft capital of the U.S., so it's inhabitants are being extra-diligent these days. Even down here in Hooterville I keep my truck and trailer locked up in the shop, behind a locked gate, guarded by a dog and an armed unsympathetic Redneck that drinks. Back to your original question, while I do enjoy my 6x10 enclosed trailer it will affect MPG on the tow vehicle due to it's brick-like aerodynamics. It does on my Cummins Dodge, as much as pulling a 25ft. gooseneck does. Food for thought.