Actually I made an 8MB partition to test with. And I used 8MB to dd the download img file.root@dev:/home/tc# df -h /mnt/sdc1/
Filesystem Size Used Available Use% Mounted on
/dev/sdc1 8.0M 5.8M 2.1M 73% /mnt/sdc1
It seems your dd worked fine.
However, I was just saying that, theoretically, it's possible, though unlikely, that dd-ing just 8Mb you lose some data, because one can't reasonably know where fat algorithm actually stores the files.
For example, if for whatever reason your mmc partition becomes fragmented, some piece of some file could end in that final 1Mb of the partition that you left out.
That's why I suggested dd-ing x+1 Mbytes, where x is the size of the whole partition, rather than only the used portion of it.
So in this case, I think the best thing is to dd 9Mbytes, or 9Mbytes + 1 sector, even better
Should I have misunderstood what you said, please ignore my whole rant.