Just had another flood due to a crimped port O-ring. It could not be seen from either inside nor outside the housing but it crimped. I had to change the O-ring for another (camera and lens survived because I am so nervous about floods now I test the housing by dunking it before evry dive.)
When I checked mt bag of spare O-rings (all the latest blue type) I found that they were slightly smaller, not in cross section but in length. This meant that the replacement fitted snugly into the groove rather than slopping about as the ones originally suppled with ports and extension ring do. In fact they fit just like they do on every other housing by other manufacturers I have.
My question is: Which is the recommended O-ring? The one that fits snugly with no chance of getting crimped as you turn the bayonet or the ones supplied with the equipment. The difference is tiny but just about enough to be able to lay the smaller O-ring inside the larger.
Do not confuse this question with one about the older thin black O-rings that came with older Subal kit. All the O-rings in question are new and blue.
This Subal housing is turning me into a nervous wreck!
Glad it wasn't terminal. 
