I think it is better to err on the side of too much tongue weight rather than too little. I was trailering two double-stacked boats to Ohio last year, and after having driven a couple hundred miles with no problem, suddenly the trailer started fishtailing badly. I was on a freeway, and I had to keep slowing down to about 40 mph to get the fishtailing under control each time it started.

So I stopped early for the night and I asked the advice of a trucker who was staying at the same motel. He checked out the trailer and said the axle is bowed down and the wheels are canted out and the bearings on the starboard side are probably going to disintegrate soon from the stress. He advised me not to drive far. I said, "Well, I have to go another 700 miles." He said, "No way. Go to a repair place and get a new axle and replace the bearings."

I did not take his advice. Instead, I decided that the boats had slid back on the trailer because of not being tied tight enough. (Not our boats and not our trailer.) Figuring the problem might be from not enough tongue weight, I pushed the boats forward a little, tied them down very tight, and had no problem the rest of the way to Ohio.