Decal aspect ratio - 512x4096 ok for performance?

I’m making some paint line decals for a road and am wondering if it’s more or less efficient to use something like a 512x4096 texture as opposed to a 4096x4096?

It appears I have to scale the default square decal actor to a rectangle regardless, but I’m mostly concerned with performance. I know some engines favor square textures over rectangular ones, but a square with 90% of it unused seems wasteful.


512x4096 is cheaper than 4096x4096.