Yes, I'm surprised, indeed it's a thousand pounds less, hull only.
Don't forget to add for motor, oil, gear, batteries, fuel, at least another thousand pounds, plus the trailer. The GVW less the carrying weight is the trailer weight - the aluminum trailers are light!
I have a Roadking RWSS-19-21TB:
http://roadkingtrailers.com/RWSS.htm
It has the tandem 14" wheels, with a 6K lb gvw.
The next size down with tandem axles has the 13" wheels, drops the GVW to 5400 which would be fine, but I would rather have 15" wheels under mine, the 14's are minimum, I just don't like the smaller wheels under a boat trailer. You would probably save $200 is all, if that. It's like splitting hairs. Trailer tires aren't all that great anyway, and the smaller wheels spin faster. I've already replace all four tires on mine, they are the Carlysle SportTracs. All of those trailers have the same frame and springs in similar gross weights, the higher capacities come with the bigger tires.
A single axle would also work, I just like a tandem under these boats. The RWSS-19-21B has the 15" wheels, single axle, with a 4300gvw and net carrying of 3550. That would probably work for your boat as well, and cost several hundred less.
Other brands may vary. :wink:
If you have the bucks to splurge, go for one with torsion axles and Kodiak brakes. The Tie-Down stuff is just so-so. And the leaf springs rust out, but they're cheap. I've got 3 years on mine and the springs are pretty rusty. I figure within a year or two will need to replace the springs and the brakes. That's about $600. And mine gets rinsed religiously after dunking in the saltwater.
The model I have should come in well under $4000 all in.
Trailers are like trucks, consider leaving a 20% carrying margin. Running them right at capacity leaves nothing to spare as it ages. They can and do break if you don't keep a really close eye on everything.
The side guides and bunks work great. I have yet to see a ramp that a launch or retrieve took longer than a minute or two. I'm usually in or out and gone while everyone is still dinking around trying to launch or load their boat.