We have used a variety of trailers to transport Sunfish. A light duty trailer will usually work if there is at least 8 feet from the hitch back to axle, that will allow the CG and weight of the boat to be forward of the axle. Bunks can be fashioned to support the boat fore and aft under the cockpit and keel or trimmed to run side to side. The best supports will be placed under the boat in areas where fiberglass meets fiberglass, examples are under the mast step, under daggerboard well and under the cockpit. The other areas of the boat are only supported by internal foam blocks or nothing at all, and a support could punch though the fiberglass. Hull down or up are acceptable, but if you race you might keep the hull up so road debris does not chip the hull. One key is to not tighten straps too tight, ratchet straps can break the boat. Another tip is to duct tape pool noodles to the bunks, they act as great cushions to dampen road forces transmitted through the trailer.
Light jetski trailers, motorcycle trailers or john boat trailers are easily converted, a leaf can be removed form the spring if needed. Trailex sells a good aluminum trailer and Harbor Freight sells a nice light boat steel trailer. Academy Sports sells an aluminum trailer and your local trailer supplier can make or deliver a good galvanized trailer, essential for use in saltwater.
From left to right in this picture are a motorcycle trailer with bunks added, the Trailex trailer and a Highlander light boat trailer adapted for the Sunfish.
12 inch tires work great for long trips, if you use the 8 inch tires and travel long distances anywhere warm, take a spare, we burned up a new set of tires just getting across Arizona in the Summer. This Highlander is perfect for local pickin trips and has a tilt feature that helps to load/unload the boat.
This small jetski trailer required little adjustment, we a added a keel roller and still need to add a bow stop. In this picture the boat is too far forward, the keel roller should rest below the mast step.
Here is a larger Magic Tilt jetski trailer set up for two Sunfish. We added two sets of trailer guides to the side and crossbeams, padded with large pool noodles. This rig made an 1156 mile trip with no problems, both boats rode great. Our local trailer manufacturer Eddie English in Milton helped me pick the parts, the key is to get steel trailer guides posts, aluminum will not carry the load on the upper deck.
Double jetski trailer.
Sometimes you need a trailer to carry your trailer :)