It would be fairly easy to incorporate such format into a menu like BAGplug (auto decompression and deletion of uncompressed files), if enough people were really into the idea.

Here are some (loosely accurate) tests of the format I have conducted on two opposite sides of the spectrum ( 16mb, 32mb, 64mb, 128mb, 256mb):

*R4DS Rom Trimmer 2.0 was used*

**Tetris DS:**

normal size - 16 mb

trimmed size - 13.1mb

compressed size - 6.4mb

compression time (on DS) - ~1 minute

decompression time - < 1 minute

**Pokemon Soul Silver:**

normal size - 128 mb

trimmed size - 120mb

compressed size - 58mb

compression time (on DS) - ~4minutes

decompression time - ~1 minute

**Pokemon Black:**

normal size - 256 mb

trimmed size - 256 mb

compressed size - 105 mb

compression time (on DS) - ~11 minutes

decompression time - ~1 and a half minutes

**Dementium 2:**

normal size - 64 mb

trimmed size - 54.2 mb

compressed size - 39.2 mb

compression time (on DS) - ~ 3 minutes

decompression time - ~1 minute

**Brothers in Arms DS:**

normal size - 32 mb

trimmed size - 30.9 mb

compressed size - 17.5 mb

compression time (on DS) - ~3 minutes

decompression time - < 1 minute

**Club House Games:**

normal size - 16 mb

trimmed size - 10 mb

compressed size - 8.3 mb

compression time (on DS) - < 1 minute

decompression time - < 30 seconds

Max compression level was used on the DSTwo, so faster compression times can be achieved using a lighter level, or if a pc application was made for compression.

The format itself is just a gzip file, with bits of the nds rom header appended to the end, so menus such as BAGplug or iMenu can still access rom information without having to unzip the rom itself.

So what my question is, is there really a need (or want) for this or are people just happy enough using trimmed roms? If there isn't much interest in this, then this idea won't go far.

Source code for the compression / decompression routines can be found here:

http://bag.nfnet.org/wp-content/uploads/2011/04/nzip-src.zip

Source was built using zlib 1.5.2