If you have space on your trailer bunks try moving the boat fwd or aft on the trailer, this could save you from moving the axles. A couple of inches\cm can make all the difference.
Pacific Trailers in Chino may have answers to some of your concerns. http://www.pacifictrailers.com/
Some additional quotes from http://www.sandiegofishing.com/buddydb/
Tongue weight should be determined by trailer and hitch manufacturer. Too much, it will sway. Overload the hitch rating. Too little, trailer will sway while towing on level ground. The ball height needs to be figured into the over all mix also. Any trailer will have a recommended ball height. Follow that height as close as possible.
...the tongue/hitch alignment and load is critical. I wuz presuming (again) that you had it level and loaded out - back to basics, homey. Park the rig on a flat lot and step back and look at it - level vehicle and very slight down angle on the tongue is what you want. Adjust your hitch height (primary) or redistribute the load (secondary) to get the angle without exceeding your tongue weight rating of either vehicle or trailer. Normally this is 300 to 500 lbs. Ideally you want approx 2/3 of total load at or just ahead of the axle (some folks say centered) - now you can start thinking about altering the suspensions. Presuming (again) that your trailer axle(s) and vehicle axle(s) are aligned, too stiff on the trailer suspension will make it hop and too soft will make it sway.