You're thinking of it in reverse. The farther the axle is to the front, the more the AXLE takes the weight. The farther the axle is to the rear, the more tongue weight you will carry. My last boat weighed 5500 lbs and the trailer was about 1200 lbs. The dual axle trailers you can actually move the axles, they are on u-bolts. I adjusted the tongue down to 250 lbs because at times I was moving it with my work mini-vans that couldn't take the weight and I didn't really care if I beat the **** out of them because they were leased. The boat towed perfectly, even at high speeds.
What you are worrying about on a fairly light single axle, the sway, has a lot more to do with the height/angle of your trailer tongue, than it does the tongue weight. A single axle trailer is very sensitive to tongue angle, especially if it angles up towards your truck. It will make it hunt around, instead of tracking nicely. That will make it tow very poorly.