Whopity:
SkyDemon does not "derive" the vertical limits of any given airspace polygon (as the original poster was asking). They are written in the AIP. In fact, they are commonly presented as "GND\FL195" (or similar) which looks a lot like "Ground < x < Flight Level 195" to me. If I am indeed "WRONG WRONG WRONG" then perhaps you could tell me what FL means in this case? Or perhaps you meant to quote another part of my statement?
As an aside, I was under the impression that the whole point of flight levels was that everybody calibrates to the same standard (regardless of what the actual sea level pressure is) so that aircraft are reporting their vertical position to one another consistently. If my understanding of this is wrong, then its a good thing I am in charge of marketing and sales rather than coding development... Regardless, I am more than happy to be corrected.