Vaulted Ceiling w/shingles, metal roof thermal barrier

I have an awkward little house in Phoenix, AZ. Imagine an A frame then cut it in half and add a little room above it. The 80's were a strange time. The majority of the roof is one big south facing plane. Brilliant, I know, lol. To make matters worse, the whole house has vaulted ceilings, very little insulation and no attic on the south side. It has a single layer of shingles from 1983. My dad and I would like to get supplies for a metal roof and DIY it. He is a contractor and Journeyman. What would be the best way to insulated it? We are thinking white tin on purlins and battens with spray in foam. Should we remove the shingles or put it all on top. I saw hard foam metal panels online, but it looks like they are only for commercial buildings. I work for a solar company now and we are planning on putting solar panels on top. Having a large south face works to my advantage for solar, but it is at 45 degrees. Weight isn't really a concern with solar, the panels are so light. But the lag bolts for the racking that holds the panels is a concern. We were thinking of an air pocket, but with bees and rats in Phoenix, it would be hard, even with netting to keep them out. The highest peak is where the air handler is, which is terrible, lol. It has no insulation or drywall in there. I am planning on adding radiant foil to the inside where the air handler is.

I have a similar home in Texas also with a shingled roof, and a vaulted ceiling leading to a small attic over two small upstairs bedrooms.

The long front roof faces east with partial shade from an oak tree, and opposite short roof faces west with partial shade. Both sides of the roof still get a fair amount of sun in the summer.

The attic has gable vents, but no ridge vent, and there are no soffits or roof vents. It gets quite hot upstairs during the summer, and you can feel the heat pushing in through an unsealed attic. Window units upstairs are a must.

Altogether with a freestanding carport and a storage building, there is about 1650sf of roof that needs replacing.

I’m in the middle of a claim and am researching metal roofs. My current plan is below, and I wonder if I would be going too far with the radiant barrier plans:

1. Replace decking with LP Techshield, shiny side down.

2. Use a peal and stick underlayment, probably Sharkskin Ultra SA.

3. Then Sharkskin ventilated deck mat, nodules up.

4. Sharkskin Ultra Radiant underlayment over deck mat, shiny side down.

5. 24 gauge standing seam metal roofing (we get hail).

I’m wondering do I really need two radiant barriers and should I skip the LP Techshield. Or, if two barriers are better than one, then the Techshield would keep me from having to get up in the small attic and staple foil to the rafters.

Any thoughts? Have I been drinking too much of the radiant barrier coolaid with this plan?

Thanks for your response. I will reach out to SharkSkin. Poor attic ventilation has been a concern. I'm thinking a ridge vent and/or low powered gable fan would help. I could have soffits cut under the west side eave but am not sure how to balance that on the east/long roof side.

If I opted to replace the shingles instead, GAF has a product called Cobra Intake Pro that I'm told could be installed on both sides of the attic roof in lieu of soffits. It might not look great high up on the top third of the long side roof where the attic starts, but with a ridge vent it should help.

I'd much rather have a metal roof though, one and done plus the energy efficiency.