hi dockdoc,

if you will be subjecting your boat to significant temperature swings, some kind of venting is a good idea, in my opinion, to keep large enclosed areas from becoming deformed/bent inwards (typically during the cold) or pressurized  (typically during the heat).  while i have not built an Oxford II, i have built some long, high performance kayaks....and its something that i think about and have observed the consequences of when i failed to consider the issue you raised.

that said, i have typically dealt with the issue by having some kind of hatch that also allows for ensuring the inside of large compartments stay dry.  the hatch can be loosened  when not underway which gives you a vent.

if you look at picture 23 out of 44 of the Oxford II page https://clcboats.com/shop/boats/rowboats/oxford-rowing-shell-II-wooden-boat-kit.html, you will see the builder, david brittany, has placed two small beckson hatches on each half of the boat.  a close inspection of other pictures will show beckson hatches in many cases. 

absent hatches, a 1/8 inch hole in the middle of a bulkhead (equidistant from the floor, deck and sides....is my standard vent.  the middle of the bulkheads is typically the place that won't see water if the boat is flooded or turned over.   however, my strong preference after a lot of years is some kind of hatch that can also serve as an inspection port and a way to remove any water.

h

Thanks much for the advice. A couple of hatches seems like the way to go. It's nice to have some way to inspect the compartment once in a while as well.    

   Btw. In my note above I should have said 1/16 th hole for a vent. But the hatches as you note, will be a better idea.

Thanks again, I think I will go wth a 4" hatch similar to the pictures in the gallery.