R4DS ROM Trim Tool
From GameBrew - a wiki dedicated to Video Game Homebrew.
|R4DS ROM Trimmer|
Since the capacity of NDS cartridge has a fixed standard (128Mb, 256Mb, 512Mb, 1Gb, etc), the capacity of the dump will have the same standard: 128Mb, 256Mb, 512Mb and 1Gb (They will display on the PC like this: 16MB, 32MB, 64MB and 128MB, 1Byte=8bits).
On the other hand, every game has different capacity, which is not exactly the same as the standard. Supposed that the game has a 300Mb capacity, it will need a 512Mb game cartridge to run, that makes the remaining 212Mb redundant. The R4DS ROM Trim Tool can delete the redundant data to save space while keeping the game run efficiently according to this theory.
Select .nds file and trim for a smaller size rom.