I have become aware that Super Mini Mario and its various mods are difficult to run on the custom 2.71 firmware from DAX. So, here's a fairly simple way to run most of them from what I can discern:
Some SMM mods are built for 1.0 and some are built for 1.5. While you can use SeiPSPTool to convert between the two, it doesn't help you much here. Here's what to do:
If your SMM or SMM Mod was built for 1.0 natively (not converted from a 1.5 eboot) then: Simply place it in the GAME folder instead of GAME150. Works great! Examples: SMM (original, non-1.5 version), Chocobo Complete, Super Mini Sonic/etc.
If your SMM or SMM Mod was built for 1.5 natively (i.e. the 1.5 version of SMM, or Super Mini Halo - SMH - which was built for 1.5): This is a bit trickier. You have to split up the contents of the SMH folder (for example) so that GAME/SMH contains all the DATA files that are NOT the eboot.pbp. So EVERYTHING that is NOT eboot.pbp goes in GAME/SMH. GAME150/SMH will contain the eboot from the SMH folder, and GAME150/SMH% is the SMH% folder without any other modification.
So this is the structure:
PSP
|__Game
|__|__SMH
|______|__(data files here such as sound, graphics, levels)
|__Game150
|__|__SMH
|______|__eboot.pbp
|__|__SMH%
|______|__eboot.pbp