Gene, I don't know how well the Zircon finder works. Thanks again for posting those sheets, that is a nice help. Someday I might put a solar panel or two on the roof and that sheet will be very handy. I have however read many reports where people don't hit any framing on the roof when they mount their panels, and the mounting is still solid when the appropriate materials are used.
Burl, I am probably over-thinking the bed platform top. The main reason I am doing that is because the overall thickness will affect how I trim out the top edge of the box. If I need to sandwich layers together or add battens or such, that will cause me to adjust my plans a little bit.