What about secrman_for_dex (vs. retail's cex), which the later TESTs have? My DTL-H30102 which has dex doesn't like McBoot (either the installer or the resulting card) much. I've heard they do boot utility discs unlike the older TESTs however.
All version of TOOL and certain versions of the TEST have SECRMAN_FOR_TOOL instead and while it can decrypt signed MG files it can't handle the bit tables so in the end the units can't really read the OSD on memory card. Maybe if we skip the 2nd layer and just slab the elf inside the OSD without the XORing it works .... lol