I'll add my insight to your thoughtful design. The reason people are advising against multiple cylinder air actuation is because it has been tried by others... and failed.
There were several times during my build... which is still not finished... where I chose not to take the advice of more experienced builders, and later came to learn that if had taken their advice I would be further ahead with a better result.
If you are set on air, I would suggest a single cylinder operating pull "cables" made of light weight 550 paracord over a nylon pulley system, configured like a traditional pop-up.
IIRC, the issue with PVC is that the pressure ratings are misleading. It doesn't like to be pressure cycled. So in a shop air environment where you are shutting down the compressor (or at least isolating the distribution system) every day, it can lead to problems. Same for a dynamic cylinder with pressure cycles. Maybe not such a problem for low pressures, but the concern is well documented. IMO, PVC should be reserved for low pressure drains and, perhaps, electrical conduit (CPVC).
Another concern is that the OEM's control the OD very closely for compatibility with the fittings, but there is a wider tolerance on the ID. Have you checked any samples for circularity on the ID? Rather than 'o'-rings, cup seals might be a better choice.
I'm not sure if I interpreted your plan correctly, but it almost sounded like you were planning to skin the "skeleton" areas and only paint the foam. If so, the foam is quite fragile and would quickly deteriorate. Plan on pmf'g the foam, too, or better yet use epoxy/glass weave. Two plys of 6 oz cloth saturated with epoxy provides a substantial amount of armor, does stay relatively flexible (contrary to common mis-belief) and, surprisingly, weighs virtually the same as 10 oz canvas pmf.
One last observation, I am concerned with the proximity of the peak of you splitter fin to the trunk lid on your TV. This gap will close when transitioning onto an up slope or off of a down slope (approach and departure angles). Yes, foam is fragile and somewhat compressible, but can sustain significant pressures over larger areas (IIRC the common pink stuff is 25 psi). So while the pointy bit might not do much harm, once it starts to flatten the contact area will increase and it will no longer yield as much. I could see it easily denting a sheet metal panel. Once reinforced with pmf or epoxy/glass it won't yield much at all.
