Brock,
Sorry not to have reported back on the clam shells off the shelf from West Marine, were too small, (Depth) for the vent. I think you may find other ones which are larger, or make one out of SS sheeting. I didn't try building up the lip with starboard, but that should work also--I may try 1/4" making a rim, and screwing the clam shell on top of that. So far we have not had a problem--but got 2" of rain today, and I'll check.
Sorry not to have reported back on the clam shells off the shelf from West Marine, were too small, (Depth) for the vent. I think you may find other ones which are larger, or make one out of SS sheeting. I didn't try building up the lip with starboard, but that should work also--I may try 1/4" making a rim, and screwing the clam shell on top of that. So far we have not had a problem--but got 2" of rain today, and I'll check.