Venting a rainscreen at the stucco weep screed – GreenBuildingAdvisor

We’re using Zip sheathing with Delta Vent S over it, and the Delta stucco and stone rainscreen over that. Climate zone 3B Southern California. This wall is getting scratch and brown then natural stone veneer, and is using a traditional FHA-7 style stainless weep screed. I’m trying to work with the current setup to vent the rainscreen but have a couple questions:

1.  To vent with the current weep screed, how would I get an idea of how many/what size holes I would need?  Would drilling those holes cause any issues with water? (I imagine I would only drill the top, under the bug screen and water would run down onto the bottom piece that’s bent back and down/out). 

2.  Since 3B doesn’t get a lot of rain, should I just not vent and use the Delta stucco and stone as a 3/8” drainage mat?  Would that cause any issues?

3.  If I don’t vent the bottom, would it help or hurt to vent the top?  Reading up on it, I see that generally the bottom is vented first then the top added to increase ventilation but haven’t seen anything talking about just a top vent. 

Thanks,

Mike