Making Time Machine work with the ReadyNAS

I've been snooping a bit, and as if following your own instructions, Time Machine does indeed create a journaled HFS+ file system -- but with a difference, since it creates a journaled HFS+ *case sensitive* file system. What are the implications of using a .sparebundle file with a presumably case-insensitive file system instead of a case-sensitive one for Time Machine? If the difference is important, how can we replicate it? Judging from the -fs specification in hdiutil, there's only HFS+J or HFSX (case-sensitive), but not HFSX+J.