Move it Back
Move the axle back. You can calculate approximately how far to move it. Measure the distance from the axle to the hitch. I assume you know the approximate weight of the trailer. The new weight on the wheels is equal to the old weight minus the weight to be added to the hitch. Multiply the distance from the hitch to the axle by the old weight on the axle divided by the new weight on the axle. For example if the distance is now 13 feet and the weight on the axle is 2000 pounds with no weight on the hitch. Then the new distance is equal to 13 times 2000 divided by 1850 (2000 minus 150) or 14 feet. Move the axle back one foot.