1) Take this with a grain of salt, I've considered using these panels multiple times, but I never have. Here's why.
The screws go thru the top of the "ridge". The panels of course expand and contract as they heat and cool. Perfectly normal, natural, and entirely unavoidable.
If the screws are secured to the purlins, then all the stress of that movement is focused on the hole you drilled for the screw penetration. That's a recipe for failure unless strips are used to stabilize that surface. Preferably hard strips, not the foam, which doesn't seem "rigid enough" to me to effectively transfer those loads.
Meaning that, in theory at least, that the closure strips are needed to maximize the life of the panels, which significantly increases the cost of install.
Same problem is present in metal roofing of similar profile. Which is why I use the "5v" panel design and screw thru the flats - but that doesn't help you with the PalRoof. Their Suntuff panel ALSO wants screwes at the top "crest", rather than on the flats. I consider it to be a defect in the design of them
If you are set on using them - and there are good reasons to do so when other means of getting light into a space aren't available - but short term cost is a concern, and lifespan is less concerning, I'd use Suntuff with its geometric hex design and flats instead of the PalRuf wave, and install thru the flat anyways. and likely thru a dense white foam roll sealing strip. Which will, of course, void the warranties.
