kinda, not really though. These are rolling lobe air springs with a pretty significant lobe (at least on the first gens, have not messed with the second gens), the spring rate does change, but not significantly until you get past the point of the inner "cone" or lobe, as you put more air in the...
It's actually pretty easy, on the second gen there's a sensor on each side oh, just need to put a spacer on it. First gen only has one. Should be able to support an extra 3 in pretty easy