Please, please, please do not buy a Rocket Trailer. They are complete junk. I had to rebuild mine from the ground up and it was only 2 seasons old. Top that off with it FLOATED when you backed it down the boat ramp. I had to weigh it down with 200 lbs of dumbells. New axles, new tires, new bunks, additional bunks, new lights, new brakes (opted for 4 wheel disc over 2 wheel drum). All I had was trouble with mine until I did this. If you want Aluminum, I would check out Allison Trailers, an OSO sponsor, also sold by Fred Cecil aka Too Old at www.TrickMarine.net
I have no experience with Allison, but everyone who has one raves about them, and they supply a lot of manufactures.
I would rather load my boat onto the roof rack of my truck, before I put another Rocket Trailer under it. You can do some searches here of my perils on OSO with my previous Rocket Trailer.