[bobsgarage]

Damn, the vaulted ceiling makes it hard to get all three feet lined up with A rafter. What I've got to say probably won't help you but maybe somebody in the group can use this information

One of my arrays has a 10 ft tripod. I had trouble lining the three legs with the roof rafters. Only one leg would contact the rafter and I had to put the screws through the roof to locate the other two legs. After I had the pilot holes drilled I was able to know where the mounting bolts would go and put two by sixes between rafters just under the plywood of the roof. Then I ran large 3/8" screws through the rafters into the two-by-sixes between the rafters. Once I was done, I re-drilled the holes for the tripod feet.

I have a truss type attic with a shallow pitch. You have to climb in and out of the trusses and there's no headroom. Even at the peak of the roof you can't stand up. I realize you have no access to your attic, in fact I don't think you even have an attic. If yours is the old roof type with one by fours under the shingles a tripod should mount to that. And like rabbit said, make sure you use the tar pads. I also sprayed mine with Flex Seal, the black tar spray can formula. It really penetrates and seals well.

Every year I go on my roof and just for the hell of it I spray each foot of the legs of the tripod with Flex Seal. If you need to go say 10 feet or more (20' mast) above the 10 foot tripod you could use guy wires to take the wind load off of the tripod.