I have finished framing a building that has an unusual roof and I need some ideas on how to apply a ridge vent. The roof is a gable with a shed dormer. The shed dormer ties in at the ridge allowing 2 different angles at the ridge. The roof pitch on the front of the gable is extremely steep 19/12 (58˚) and the roof pitch on the back of the gable (Shed Dormer) is about a 7/12(31˚). I have sent emails to some plastic ridge vent manufacturers (ex. ShingleVent II) and they claim their vents will go to 16/12; any higher and it will leak. Gable venting is not an option on this building. The roof will also be covered in Architectural Asphalt Shingles.
If the manufacturer is telling you their plastic vent will fit over a 16/12 pitch, I think it would probably work in your situation. You are a bit steeper on one side, but not as steep on the other. When you average the two together, it seems like it should work. The only other thought that comes to mind is the cobra ridge vent that comes in rolls.