I recently started using an 02 F150 for towing my boat. The truck already had a leveling kit when I purchased it. My problem is when I'm towing my boat, the front end of the truck feels squirrelly. If I catch a groove in the road, the truck takes off and follows the groove. I have rebuilt the front end and had an alignment done. The guy that did the alignment said the front was slightly higher than the rear. I'm pretty sure that's what is effecting my towing. Question is would over load springs or add a leafs help correct this problem. FYI my boat is an 01 Cobra 201D.

Weigh your boat and trailer, off the truck. Then use a set of bathroom scales and weigh the tongue. That will tell you the percentage of weight on the trucks bumper.

Lifted a Tacoma that required a different tow than factory specs. Went from slight tow in to zero tow. A tow in can make the steering squirrely.

If the rear of the truck is lower without boat attached then with the trailer attached it will be extremely lower. Add a leafs will help.

Lesson number one to never level a pickup.

bass_n_fire, I just bought an 05 F-150 and I have it lifted 6 inches, with a very slight "ghost trailer" or "cali lean" or whatever you prefer. Basically the rear is slightly lower than the front like yours. The rear is just blocked. Have so far had no problems towing my 19 foot tandem axle boat, haven't towed very far yet so I'll update you on a long haul, but it seems solid, no steering difficulties. Seems as if you might have too much tongue weight? I'm no expert, but that's where I'd start, too much in the back might make the front jump around. I made sure with mine that I had the drop hitch that put the trailer perfectly level. After that, I'd say add a leaf or just stiffer springs is probably your way to go like you said. My 2 cents