Well, the weather did NOT hold.  I first set up under the canopy, but when I looked at the weather radar, I moved about 100 feet to the porch.  Sure glad I did.  I had played four songs when the storm hit.  I had the tarp ready and quickly unplugged everything and covered it just it case the wind blew the rain across the porch, which it did to a degree.  Lightening was pretty bad for about half an hour.
After around an hour the rain stopped so I uncovered the gear, plugged it back in and started playing.  I played one song and the power went off.  
There were about 50 people there, so I hung around for three more hours, ate the food, drank the iced tea and talked to the folks.  Then I loaded up and came home!  Almost $100. per song.  I felt bad about it but it wasn't my fault.  I gave them a $100. gift certificate to Ernest's as a goodwill gesture.  They told me not to feel bad because it wasn't my fault and they would call me for Labor Day.
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DonM