The way the ipl does the backup, the rawnand.bin DOES fit on an empty 32gig card, because it's slightly smaller than that. You then separately get BOOT0 and BOOT1 partitions, which are small and distinct from the main rawnand. Now stop saying it doesn't fit when evidence and experience shows otherwise.
Maybe it's one them thur 16gb - 32gb sd Chinese hybrid cards . Can you saturate that space successfully with a file transfer in widows ?? I used 32 gb SanDisk full raw nand fits.