[kingdaddy]

Good question and one I've wondered about too! I plan on getting some before and after weights on mine to see how that works out.
Seems like if the pivot point was the rear axle and the pin was centered directly over it the weight difference on the front axle would be nil. But the rear leaf springs attach to the frame both in front of, and behind the axle so the weight distribution on the frame (and therefore transferred to the front axle) could vary somewhat. Also, if the pin were even slightly in front of, or slightly behind the rear axle it could add to or subtract from the front axle load fairly quickly.
Theorizing aside, I agree with H. John that the only real way to know would be to actually get some actual weights. Kinda interesting how his weight distribution changed with the two different trailers!