[DanEC]

I agree with Doug that the Girling cans are a bit of a pain and fragile but installing Dorman seals in the lids has taken care of all issues of leaks for me. I keep the cans just over half full and with the lid seals I don't have any leaks. When I remove the lids I usually find the lid seals are slightly distended indicating a good seal. The connections at the bottom of the cans have been a bigger issue. I re-sealed all of my cans with some good sealer in addition to the provided gasket washers.

Edit - to give credit where credit is due:

Patrick came up with the girling can lid gaskets.

ERAChase suggested using two hose clamps at each rubber line connection to the steel brake lines - with the scew tensioners spaced 180 deg apart - to prevent leaks.