Hi there, good points on firewood. I know IN doesn't allow firewood in from other states. But back on topic, assuming you wanted to add storage to the back of your TT.
Here's how I added storage to the back of my trailer.
Regarding the weight transfer, your math is a little off. The "moment" or the force exterted, is equal to the weight x the distance to the fulcrum. In your case the fulcrum is the axles. You say your axles are 2/3 of the way back on the trailer....so the distance from the axles forward to the tongue is twice the distance from the axles back to the bumper. That means that 300 lbs added to the back will reduce tongue weight by 150 lbs, NOT 100.