I don't have any dimensions, but there are some photos of the trailer on my album:
I have a second Cat trailer for the Caracal 18 feet--which is also aluminum, has a similar bow stop, and center bunks.
I do believe that the aluminum trailers are better--they are lighter, they have less corrosion/rust, and are open, so no hidden tube damage. Torsion axels get the boat lower--
The trailer I had was capacity of about 12,000 lbs. We had the two 16" wheels, instead of 3 14 to 15" wheels. Much less scuffing that a 3 axle trailer. I like having both side bunks and the center bunks--be sure that the center bunks are substantial welding.
The actual bunks were two 2 x 6, slightly V, covered with carpet. The spacing you can get off the boat or factory. You want the center line between he two boards at precisely the center line of each hull.
The forward stop needs to be very strong and well braced. Just one stop does not cut it. Electric over hydraulic brakes I would say are almost mandatory for West Coast trailering. Be sure and put some form of a ladder for boarding the bow on the bow stop.
Put slicks on about the front 1/3 of the trailer. Be sure and strap the stern, and have a hold down chain or turnbuckle for the bow eye as well as the winch strap.