mh maybe i got something wrong but a 2048x2048x16 texture is four times 1024x1024x16, so it mean you can load 8 1024x1024x16 or 2 2048x2048x16 instead :>

thats why i wouldnt go over 1024x1024 unless i really need to

as traveler says the format doesnt matter for memory usage, its only for filesize