Could it be that it’s been some time since you checked that thread (I assume you mean this one: PC12 Pressurization/Oxygen System Broken )? FL140 is only mentioned once back in December with the info that it’s safe, but not necessarily the upper limit. Findings after that date (including confirmation by myself) show FL200 as where the problem starts, I could cruise at FL198 (yes, one niner EIGHT) without problems (but that could change depending on air pressure, so you should stick to max FL190).