It really depends on your vehicle rear axle and spring capacity. If your have reserve and your truck is sprung heavy, you may find it rides better with more weight over of behind the truck axle. If you are getting sag, you should try to locate the heavier items farther forward in the truck.
Some trailers will track well with only 5 percent tongue weight, but most need 10-15 to be stable. I generally try to pack the heaviest items in a trailer over the axles or just slightly forward if I have stability problems. My enclosed trailer holds five 60 lb batteries in a PowerArmor battery box on the tongue. this gives me over 20 percent tongue weight when empty and I can load the trailer tail heavy without concerns as long as I try to keep left and right weights evened out.