I spotted this trailer on Craigslist last night, wrote to him, but not sure if it will work for the Weekender. He says "the model" (maybe he means the boat in the pic) is 14 feet and the trailer is 16.5.
http://sfbay.craigslist.org/eby/boa/388386684.html
Seems to me I've heard that a 14' bass boat trailer works for us.
Don't know much about trailers and I haven't fitted my half built weekender on my trailer yet.... but... from the picture of the trailer you are looking at you will obviously need to make taller bunks so the keel has room. Other than that, I think the trick is to be able to "balance" the boat over the wheels so that the tongue weight is not so heavy. In order to balance it out, you almost need the wheels to be toward center (not towards the back of the trailer). Some trailers seem to have long tongue areas with the wheels at the back, which you would have to "hang" the boat off the end. Unfortnately with the picture they show on Craigs, it is hard to say if this is the case or not. It does kinda look like the wheels are at the back. You would likely need to add higher and longer bunks. Not sure if the above is helpful...I would wait to see others responses.
Most all trailers are designed for the most popular boat type in the country, which is a 14 to 18 foot, outboard powered frozen snott ski/fishing craft. This type of boat has the CG well aft (outboard, tanks, batteries, etc.), so the wheels need to be at the back of the trailer to get reasonable balance and tongue weight.
Sailboats have their CG much farther forward then power craft, so the wheels need to move forward on the trailer's frame rails. This is usually easy enough as most are designed to permit the axle/spring assembly to move back and forth, often times in a tray with predrilled holes. Bunk arrangements, keel rollers and other assorted details can be worked out in an afternoon.
It's hard to tell from the photo, but it looks to be a box section galvanized trailer (the cheapest and most common type), which may be a "broken back" (tilt) style. The deal looks pretty good as you'll get an aluminum boat, outboard, tank and a couple of sets of oars (my assumption from the wording of the ad) and it surely will hold up a Weekender. Not bad for a few hundred bucks.