[Yaffs] Reserving system space with YAFFS2

I'm looking at using YAFFS2 on a 256MB flash part where we'll be
setting up Linux with a 56MB system partition and a 200MB user
partition. We need to do this to protect the system, since there's no
way to keep the user from filling the flash, and we need to reserve
some space for the system services and component updates.

Would it be better to just go with a 256MB partition and setup the
user space as a preallocated loop-mounted file? That would allow
wear-leveling to work for the entire part, but I think the
inefficiencies of putting another file system on top of YAFFS2 would
be pretty high.

I didn't see any sort of "reserve space for root" feature in YAFFS2
that some other filesystems have. Did I miss something obvious?

Thanks!