Ho Hum, you are usually pretty good at this stuff englishal, must have been a bit of a heavy night
If you are instrument training, the person in the RHS has to be an instructor and so can log PIC for the whole lot because the regs say he can.
Now what's that about not being able to log PIC when you are training for your IR and from the instant you fly into a cloud....... The only time I can see that is the case is if you get all scared and suddenly stop manipulating the controls...
You can log PIC if you are sole manipulator of the controls if you are rated in the machine (because the regs say you can), if you are an instructor (because the regs say you can), and if you are responsible for the safe conduct of the flight (because that sort of makes sense, as you are in command). Nowhere does it mention weather (and don't give me any IFR stuff, you can file and fly IFR in severe clear
)