It should have complained I guess, when operating with pounds. My 40600 (kg) would then lead to a ZFW being lower than the empty weight of the 737 if the gauge reads the value as pounds. I don't know if that check is modelled though. Works the other way around too.

But, still, good question. Maybe it just calculates right away, we could check that with some out of range values. My guess is that the PDCS is metric on the weight values Either way, that information is vital of course.

Some folks with a VREF table for the adv, which should be slightly lower than the on the normal -200. http://www.nordicair.org/la/737land.htm It supports your idea of the imperial units in the PDCS.