What does the front of your trailer look like? Most of the time, place where the bow pulls into the roller is adjustable, both in height as well as for to aft. Typically it is held on by U-bolts. Normally you just unbolt the U-bolts and slide it forward. Since you implied that you can weld, cut it off and weld it in the new location. I'd much rather see you move the boat forward than mess with the axle. As soon as you start messing with the axle, then you introduce alignment issues. Trying to weld upside down under the trailer can be a bit of a pain.
One caution I would add. While one can never have too much tongue weight as far as handling is concerned, most trailer tongues are not designed to support a lot of weight. They are designed for pulling. Too much tongue weight could cause the tongue to buckle on a large bump or hard breaking. Most the time, the trailers are heavy enough, but occasionally they do buckle.