Nice work. The obvious problems with DCM have been fixed in ndefpack.
I've been testing ndefpack quite a bit and found a small problem.
When adding 4k cartridges such as HesMon (yes, it is only 4k) ndefpack crashes when saving the new .crt image. DCM fills the extra 4k with ($FF) bytes.
Here's a link to the 4k
HesMon.crt_________________
Ray...
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It's OK if you don't agree with me, I can't force you to be right.