Enclosed Car Trailer Question

[big gear head]

I'm new to the enclosed trailer thing. I bought my first one last year, and I don't know much about them. I was told to get the 5200 pound axles with brakes on all wheels, and that is what mine has. I passed up an aluminum trailer because it was about 4 feet shorter than what I wanted, but the lighter weight would have been nice. Mine weighs 3400 pounds, and with my 3600 pound car in it my truck is working very hard to pull it. I'm amazed at how much harder it is to pull the enclosed trailer over my open trailer. The enclosed trailer is hard to pull even without a car in it.