One important thing I realized from all this discussion is that tongue weight is only a small part of the story. You also have to consider your vehicle's specs regarding the load on the vehicle’s axles. If your tow vehicle can take it, there's no absolute reason to keep tongue weight below 10%. Other factors are equally important.
The "pro" at the Caulkins Boat Trailer distribution center recommended leaving everything right where it is, or moving the bowstop (and boat) 3-4 inches aft at most. The tongue weight is 225 pounds (you have to put the scale right under the coupler and have the coupler at the same height as when it's hitched-up to the van).
My vehicle's suspension and hitch can handle a tongue weight up to 200 pounds without a load-distributing hitch, and up to 350# with a load distributing hitch. The fellow knew the gross vehicle axle load limits for my van and said everything was nearly perfect. (He tows his powerboat with the a Dodge Grand Caravan, just like mine with the towing package.)
He had two recommendations, but he said it was really just fine tuning: move the bowstop a tiny bit to lighten the tongue weight by only 25 pounds, and load the van with a more even distribution of weight.
He estimated that moving the bowstop aft 3-4 inches would change the tongue weight to about 200#, which would get it precisely just under the manufacturers recommended range for a non-load-equalized hitch. He said to try moving it the next time we had the boat off the trailer. It's quick and easy, just loosen four bolts.
He pointed out that the trailer axle is positioned just behind the keel, where it should be to prevent fishtailing and lifting the front wheels off the ground. He wouldn't consider moving the axle for our trailer.
He said we could move the bow anchor aft to lessen the tongue weight by 25 pounds. Easy fix.
Regarding slipping on the ramp, he recommended checking the weight distribution between the front and rear axles of the van to fine tune things. The max load per axle is 2700 pounds. He recommended moving the cargo inside the van so that move of the weight is forward if the loads between the two van axles differs significantly. He advised us to carry the OB in the middle or front half of the van, not at the back.
He also mentioned measuring the front and rear bumper heights of the van without a load or trailer. And then load the van so the bumpers are evenly lowered with the trailer hitched up. When we put the OB on the transom for launching, this will lessen the tongue weight, and transfer more weight to the front wheels for traction on the FWD van.
He said use low gear for pulling the boat out.
Thanks again,
Judy B
1985 WWP19 #266 Redwing
Sailing SF Bay