Sven (and all other users interested in Neomax 1.5):
Upon closer observation of neomax 1.5, I found a bug (that cory confirmed) using the format function.
When you format the cartridge (the 'sd/mmc support' button is in fact enabled already by default -- if you look really closely, you will notice a tiny upside down arrow symbol in the box).
However, if you click on that tiny box, the tiny arrow symbol will be replaced by a square black mark. That is where the bug is.. It shouldn't turn black at all -- the box should be cleared instead, so there is no tiny arrow symbol.
So to summarize, 'sd/mmc support' IS in fact enabled by default.
Clicking on the square (making it black) actually TURNS OFF 'sd/mmc support' (this is a bug -- the box should be CLEARED instead)
Now, in case you are not already fully aware of how neomax 1.5 functions, when you enable 'sd/mmc support', you can add NDS, GBA roms, and homebrew as well (though my homebrew didn't work) to their corresponding folders on the SD card, by using the sd/mmc tab. Save backups are then stored in their respective folders on the sd card.
If you disable 'sd/mmc support', the saving backup space is created on the flashcart instead (you select the size of the Save Management Support (SMS) space during format).
For either option (enable or disable 'sd/mmc support'), you may also 'add' gba AND nds roms to the flashcart on the Neo-Flash tab (these rom titles will be listed under the moonshell application). After you are done adding everything, just hit the 'multi-write' button to burn all of them.
Finally, re-connect your sd card and flashcart to your ds, and turn on your ds to run the neomax multi-loader application. Gba should run fine (using the gba loader tab), some nds commercial roms should work (using the nds loader tab), and homebrew should generally function as well (though mine wouldn't flash to the cart or copy to the sd card for some unknown reason).
However, I couldn't get saving to function correctly, so that may still be broken.
The future neomax program should hopefully fix all these bugs and work quite well, even for mk1 users.
BruceG