90% of the weight should be on the center bunks...
not directly on the centerboard or the side supports. What i did is used a (2) 10 ton bottle jacks and lifted the boat off of the trailer so i could pivot the centerboard by hand and it was just floating there, then i put the edge of the inside bunks about 3 inches off of it. The ballast, about for the boat is right under the floors so that is the best place to support the boat. Then i put the side bunks up. I basically just pressed them against the hull with moderate pressure to take the lateral loads such as going down off ramps. I triangulated all of the supports, it might be over kill but i don't want a failure while going 80 on the Jersey Turnpike. That is how i did the bunks. As far as the axle goes, there currently is a single 6000 pound axle on it now with drum brakes which i am not to fond of. I plan on ditching that setup and putting (2) 3500 lbs axles on it with disc surge brakes. I priced it out at Northern Tool and the dual axle setup including brakes, hubs, rims, tires, and hardware comes out to less than $1000 shipped. I'll be putting pics up once that is done. At that time. i also will be making a mast raising system for the boat that will be built into the trailer via electric winch. I currently am living in Rhode Island now, and the boat and trailer is in Bristol CT in storage. I might be going home to work on it soon, and when i do, i will take some pics. on a side note i also left slots in the bunks to accommodate a sling to lift the boat onto a trailer. Since i did such a good job with that trailer. I think i might take an heavy duty trailer and make adjustable bunks so i can transport boats in the 20-30 foot range this summer if i get some time on my hands.