To flip individual channels, hit the lil cogs icon next to "Normals" in your last screenshot. Y should be green unless you're mistaken. Please be patient while I practice my gas lighting effects. As for the idea itself of using non-square textures generally, TIL it's no longer a bad idea to do as long as you stick with…
I'm using Marmoset Toolbag as my primary texturing tool and I am very pleased with it. However, since I make game assets, I want to experiment with making my trim sheets in a rectangular textures rather than square as 1024x2048 to save on the number of texture files used. I attempted to set this up when baking, but all…