After losing one of the original fiberglass dorade vents due to a wrapped jib sheet, I purchased the large stainless dorades to really push some air through the boat.  My local fabricator made the guards and handrails to my drawings and specs.  They were as expensive as the vents themselves, but have saved any more dorades from the float test.

Ralph Richardson
TERRA NOVA
T-37 ketch #406
Portland, Oregon