We tried another strategy for the leaky, high-tech vent and chimney seals. We surmised that water must be backing up under the standing seam of the adjacent panel and so caulked the entire seam up to the ridge. This was done several weaks ago, but with no significant rain in months, there has been no real-world testing.
But on the 16th and 17th we had a small amount of rain. Truth to tell I was affraid to look, but lo and behold, not a drop. It will take passing through a major storm till I'm really confident, but we seem to have licked this one.
Meanwhile I was able to create a makeshift hook-up my 300 gallon holding tank to the gutter. In the little bit of rain collected a week ago, the roof yielded 275 gallons. In the rain we had over the two days this week 200 gallons was collected, even though the downspout detached one of those days. The collected water has been used to test the DWV and mix the concrete for the porch footings.
An unexpected benefit of the roof design is that when it rains the gutter acts as a water chime.