Those psd files are that resolution because we use Foo's super high res skins as the base for our killflags. If you're using one of his skins (or any other that's 2048x2048) you should be able to just paste the base skin texture behind the emblem for a high quality skin. You can find his skins at
FooFighters Silent Hunter 4 sub skins page.
If you want to use the existing textures, then you could resize the psd file to match the skin size.
I forgot to mention earlier that, when I save to dds, I have PS create mip-maps. I've heard (long ago, in a galaxy far away), that saving without them makes the emblems disappear at distance. I never experienced, it but..........
I also forgot to mention that if you would like a skin that changes from the early war black to the later war grey color, you can combine skins. Take all the ..T01 and ...O01 files from the black skin and the ...T02 and ...O02 files from the weathered or clean skin and the skin will reflect the paint scheme used at a particular point in the war. Just make sure they're in the same places they were in in the original skin.
Thanks for the props on RSM, I'm glad it's doing it's job for you