I don't think I understand your question completely, so I don't think I can answer it fully. However:
We've all seen the tautliners on the motorway with their curtains sucked inwards (ooooh err!), this being due a partial vacuum forming inside the trailer because the air is being drawn to the outside, because that's where there's high dynamic pressure, i.e. relative wind, i.e. lower static pressure.
I don't think this is a good example. Due to the boxy nature of these lorries, the airflow around them is far from laminar. Particularly close to any sharp corners. This turbulent air creates localized areas of high and low pressure, leading to the bulging outwards and inwards of the fabric.
Same principle explains why, in general, the 'cabin altitude' of an unpressurised aircraft is usually slightly higher than its true altitude. Due to relative motion, the air is moving much faster (relatively) outside, giving a lower static pressure, therefore some air from the cockpit/cabin will be drawn outside.
I'm not sure whether this is generally true. However, I'm equally not sure whether there are any certification requirements with regards to cabin altitude vs. formal "static" pressure altitude in unpressurized aircraft. I guess the pressure inside would depend most on where the gaps in the hull happen to be, in combination with the exact location and setting of the fresh/warm air inlets. If the inlets are mostly at the front, and there are very few outlets at the rear, pressure inside will be higher than ambient, and vice versa.
The only thing I have seen in POHs, in this respect, is a correction factor if you need to use "alternate static" for some reason, and alternate static happens to vent to the cabin. In that case there's a specific configuration you need to use (DV window closed, all air vents open, for instance) and a conversion factor to get to the real (pressure) altitude.
On the other hand, I know that the location of static ports is very critical. Their location needs to be determined through computer modeling, or through a lot of trial and error, to make sure that the static pressure as measured in the pitot/static system, is as close to reality as possible.
In most cases this actually requires multiple static ports, to equalize out hull effects in all flight regimes. And even then things like sideslipping will upset the static pressure inside the pitot/static system to some extent. (Though still less than dynamic pressure.)
Note that all this applies to typical spamcan speeds. Once you get close to Mach 1, there are all sorts of transonic effects. I'm happy to say I know nothing about those.