Oh Geezzz,
These threads drive me nuts. Ok, Midlifeflyer, let me get this straight; your NOT in the aviation industry but your offering advice on a very industry specific topic? Don't understand that at all. I'm not getting' on your case here man, I'm sure your a great guy, so don't take this personally. I just don't think you should be offering advice, at least not on this matter. Just my opinion.
Everyone thinks they have the right answer.
Well, let me tell y'all something, you can't get all the right "real world" answers from the FARs. I hate to say this, but JT is right! (JK man)
I would venture to say, if you don't have experience dealing directly with the feds and employers on this issue,,,,,DON'T offer advice. It's really confusing to the person trying to get a decent solid answer.
In part 91 ops. it doesn't mean a damn thing if the airplane is certified for single pilot ops. If the operation calls for a two pilot crew (passengers require it etc.) then you can log the time as SIC! PERIOD! Now, that doesn't mean every airline is going to accept this time. Who cares if they don't accept it, they're certainly not going to tell you it's "illegal" to log it. On the contrary, I don't know of one large or small 135 operator who won't accept this time. It's good to go. One more exception: If you're working in a part 135 op., you must have a 135 SIC Checkride (8410 letter) on the books to act as an SIC and log the time as such.
PsCraig, to answer your question: If you are flying in the right seat of the Moo 2 in a part 91 op., then you can log the time as SIC, as long as you can convince who asks that you were required per the operation (passengers required two pilots for the operation to exist). You also need 3 takeoffs and landings as sole manipulator and familiarity with the aircraft systems and operations. Like I said above, if it's a 135 op., you have to have an SIC checkride by a designated check airman or FAA inspector (8410 letter). I hope this helps.