ext2/3/4 group size

[Yioryos Asprobounitis]

I was wondering if it makes any sense when making an ext fs on an SDcard to try to align the erase block of the card with the ext2 group size. 
eg assuming a card with a 4KB pages and 4MB erase blocks, try something like `mkfs.ext3 -b 4096 -g 1024'
Could it offer any speed advantage in garbage collection or just tax the file system with the keep-up of 1000 groups (for a 4GB card)?
(If I got it all wrong, please explain :-)
Thanks