Greg is correct about the reach rods going from deck to valve. I didn't mean they were all one long rod, they were a series of rods. For one thing, the deck valve wheels may not have been directly over the valve at the bottom of the tank, so needed universal joints.
As for the cargo tanks venting to the mast, if they didn't, what are the 6-8" lines that come out of the ullage tanks and head toward the catwalk? The kit parts and pictures also show vent lines going up alongside the mast.
In the "old days" before closed systems, we did open the ullage tank tops as Greg describes when loading or discharging. In that case the vent is right out the ullage tank top to the deck. Maybe the other lines are to allow air to escape or enter as the oil expands or contracts with temperature change. In that case the vent lines wouldn't have to be very big.