General rule: Sales men lie, however ....
You need the weight on each axle when loaded for travel to know if yours is to high. If the rear axle is carrying 100lbs more than the front then you may want to level the front OR add weight to the front of the trailer.
I travel with my front about 4 inches high, BUT my axle weight is greater on the front axle by about 50lbs. I have checked this at the scales several times. I carry the fresh water tank full and I also carry batteries, a compressor, tools etc in the front end.
Now when I am towing the boat I suspect the rear axle is heavier but I have never tried to weigh the individual axles when pulling doubles.