Wildtoy,
Sounds like a fun day out. Great to see Sydney Mozzies out on Botany Bay again.
Pretty bloody good to only have a cup full of water in each hull after 4 capsizes. <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> I have a cup full in each hull and I don't capsize. It's probably getting in at the inspection hatches even though they are done up tight they still tend to leak. They might not also be sealed to the decks.
The other possibilities is a small leak around the centreboard cases with all that pressure applied by the water against baords and transferred back into the cases.
Another possibility is right on the bows (although it's more usual on composite boats). A very small hairline crack can weep under the applied pressure. Try putting tape along the bow edge as a quick trial to see if it makes any difference.
Regards,
Peter