just wanted to post up here with my findings as well.
I have a Kingston 512mb SD card that boots into bootmii instantaneously. The downside being of course not enough room to perform the nand dump. Good news is that i can use a 2 card method.
I use the 512 card to boot into bootmii, and then take that card out, insert my Kingston 2gb card. Then proceed to go into the nand dump and write it to the 2gb card. Voila perfect dump, no bad blocks! Safely stored away for backup.
The reason I had to go this route simply was because #1 the 512mb card is too small for the dump and #2 the 2gb wont boot, but works perfect in every other area.
So with that all said, im now happy as I feel alot more secure in messing about from here on out. Cheers.