Hmm...I don't know if this is actually a concern for nowadays game engines, but what if a certain game engine does not support textures in that ratio? Or is it just generally accepted nowadays that next-gen game engines (UE3 for example) that it will be accepted, as long as it's ^2 size textures?
Hey odium, thanks for the pm about the engines and texture sizes man! However, I'd still love to know how you produce your spec maps! What's your workflow??