Flyingwrench.
The 1900 has become quite a contentious issue at SACAA.
Reason being, (no, I have not personally seen it), there is a factory supplement that came out a while ago, stating that the 1900 C & D are a 2 crew where there is 9 pax and more.
There is also an AIC out, (long standing), that also makes both the C&D multi crew in SA with 9 pax and more, which then does away with the single crew policy.
There is a meeting on the 16th, where this will de discussed/debated/argued in great lengths as to who is right and who is wrong.
Apparently, (hearsay), the FAA and ICAO are adopting the SA policy of anything above 5700kg being Part 121.
Sorry that I cannot be more clear on this, but after the 16th will be able to give you a more permanent answer.
Goffel