I've got a Trailstar boat trailer for my 17' Grizzly jon boat. The tongue weight seems to me to be excessive--at least 150lbs, and maybe more with the trolling motor battery in the locker. It would make sense to me to move the axle forward on the trailer a couple of feet to change the balance point and decrease tongue weight to something reasonable--say 75-100lb without the battery. It looks like a fairly simple operation. It would also help launch/retrieve the boat from short ramps.

Any thoughts or tips on doing this?

actually, that is probably pretty good. it might even be better a little heavier (around 200). if you get it too tail heavy it will be very hard to tow and will wander all over the road behind the truck and cause major swaying.

Most boat trailers are designed to be adjustable at the front upright, the part that holds your front roller and winch. Loosen it up and move it forward or back to adjust how far the boat goes on the trailer.

Let me caution you on one thing when you start moving the boat on the trailer.  Denpend on the type hull and trailer, you may have to go back under and adjust all the bunkboards/rollers.   When you change the hulls position, the bunkboards or rollers may not be supporting the hull the way they need to be, causing the hull to develop a rocker, or they could be putting too much pressure on the hull in certain areas, causing the hull to develop a hook.  You might think that fiberglass is real stong but it will get out of shape on you real quick, same with the tin cans.

Ben,

My boat is an aluminum jon. Can you see any similar problems with that material?

The other thing to keep in mind is that your adjustments will be measured in inches, not feet. A 3" adjustment will make a big difference. A 2' adjustment will throw your trailer completely out of whack. Believe me, I speak from experience. Most people want to over-adjust the first time. Try leaving the boat a few inches back from the front stop the next time you load it up and see where it needs to be in order to balance out how you want. I'd recommend about 100 lbs tongue weight for a rig your size.

Move the battery to the back of the boat, As was stated above a 3" move is a bunch, I adjusted my boat back 3" and got a sway right off. I have about 150lb of tongue weight mainly because I extended the tongue and used heavyier tubing, It does help my light truck get up the rame withouit spinning the tires.

Thanks for the suggestions guys. I'll probably experiment with moving the axle up perhaps 1" sometime in the near future.