Mounting ext4 from an ext3 system

[rikona]

I'd like to run Ubuntu with dual boot to an existing Mandriva 2008
using ext3. Each will be on its own HD. Ubuntu apparently wants to
format with ext4. Google info seems to indicate that, under certain
conditions, ext4 can't be used with, or even seen by, an ext3 system.
Will I be able to mount an ext4 partition from a running Mandrive/ext3
and do reads/writes to the ext4 with no problem?

I realize ext4 is backward compatible, but I prefer to be able to work
in both directions as needed.
  
If this will be a problem, is it possible to install Ubuntu so it
formats with ext3? I didn't see mention of that option in the install
documentation.

Thanks,

 rikona