So all this seems to center around center of gravity and I can't come up with a experiment for that right now. But I did do a test that seems to call into question the weight shift idea.
I got out my trusty gram scale and a eight inch steel rod. I supported each end on the very end while level, one end on the scale and the other to a small adjustable height table from a chem lab. I recorded the weight of the scale end while level. I then elevated the table end about 15 degrees and recorded the scale end weight again.The area of contact on each end of the rod was the same for both times. Guess what, there was no weight difference. I admit this was a redneck test but it showed me something. That something seems to mean you need a much bigger angle to expect any kind of weight shift.
Still trying to get a grip with the increased tongue weight by raising a mere inch. Just does not compute for me given my redneck test.