I tried to recreate the Helios flight problem the other day and left the pressurisation switch at manual, expecting the warning horn to go off - it didn't ! As an experiment I then opened the main door at FL330 - no pressurisation warning. Is pressurisation not modelled then ?

Minimal modelling, no alarm, cabin pressure gauge is very simplistic (i.e., take-off from Denver gauge will start at sea level, etc.).