[Yaffs] nReservedBlocks question

Hello,

The minimum blocks for YAFFAS is 9 blocks.
If I change 'dev->nRservedBlocks = 5' to 'dev->nReservedBlocks = 4' in
the
yaffs_internal_read_super function, what could be the side affect?
Do I need to change any other code if I change nReservedBlocks as 4?

I need to have two YAFFS partitions: one size is 128K (8 blocks) and
the other size is 64MB.

Thanks,
Chung