No, please reread what I said above, I never tested anything about 4 MB except for those two times I did by accident, but aside from that, I never once did it again, all ROMs I test have been between 0.5 to 4 MB, but that doesn't matter, because some games were still broken as hell when it came to audio or simply refused to boot at all. Even when it was less than 4 MB or 3 MB or whatever, it refused to boot, just a black screen, as posted in my test results above; the reason I mentioned Super Metroid is because some games that don't work via DKC seem to work fine in Super Metroid as a base. If my words confused you, I apologize, that wasn't my intent.
I will sum up my results below:
Donkey Kong Country is 4 MB in size, all the ROMs I've tested
never exceeded this size, but regardless of this, not all ROMs within the limit worked.
I will be testing Super Metroid next, which is 3 MB, as some of the games that didn't work with DKC seem to inject just fine
That's what I've been trying to say, it was only those two times I accidentally loaded those two 6 MB ROMs, other than that, I've been careful about what file sizes, and still not every ROM loads perfectly. Why, I really don't know.