If hickory is all you have, since it's stronger, just go with less-- about 3-4 chunks total. Technically not BRITU, but I doubt a lot of people have easy access to white oak, anyway.
I fooled with baby backs and BRITU about two years ago (only cook spares now). I have a preference for hickory so I may be biased, but I mixed some hickory and cherry woods with BRITU and they were some of the tastiest back ribs I've cooked to date!