@Tim: I guess you need to learn how the encryption and KELF-Resigning for MC works.
Neme's Embed-Tools might be interesting for you.
Most of the interesting and (for you) relevant stuff, including pictures which explain the structure/resigning are in the "FreeVast Continues"-Thread inside the FMCB-Subforum (the first up to 20 pages, but you can skip a lot of posts).
So,... A short explaination.
The MC-Hardware-ID (NOT, what is called "MCID" <-- This is the final KELF-MC-Key) can be extracted from any PS2 regardless of its MG-region.
The "MCID", which is generated relies on a few things.
Most important to know for you.
If all DVDELFs you have were from a different region, but still byte-wise exacly the same size it should be possible to generate a valid MCID for your other region PS2.
The generation-process is independent from the PS2, but you need the MC-Hardware-ID (no way to read it without a PS2 as of yet) which is why the entire process is done now on the PS2.
Another reason why it is entirely done on the PS2 is, because the DVDELF.bin must be decrypted in some way.
That is a rather short and incomplete explaination, but you canīt expect all knowledge in 3-4 sentences.
Neme and Jimmi are those, which can explain it best.
Read a bit in the forums.
Read about Neme's Embed-Tools.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux