I figured as much when I saw the 6061 aluminum stock and the way the axle slots and bracket offset where milled. I wish my a axle was built the same as yours. I would have copied your design!
The frame on my trailer is really light and I'm not sure about welding an axle seat on a rubber insert torsion axle. I'm afraid it would melt the torsion bushing. I'm going to weld in frame supports and lift blocks using your idea, actually after my internet search your method is saved in my PC for reference, Thanks!