Roy Smith wrote:

If you are not instrument rated, current, etc, it's not legal for you to
act as PIC under IFR. You can file the flight plan (i.e. type it into
DUATS, dictate it to FSS on the phone, etc) but put your instructor's name
down in the PIC box.

I agree. Only problem is that the official flight plan for doesn't say
PIC in the box, only "pilot's name". When I was working on my IR, my
instructor erroneously had me file my name, because it was assumed that
the instructor would be PIC. Made sense at the time since I was a
pilot and I was filing the flight plan. I was instructed that I could
file whatever I wanted to, but that I had to have an IR and meet
61.57(c) in order to accept the clearance.

After working on my CFII and investigating it further, I actually read
91.169 IFR Flight Plan: Information Required" which points to 91.157,
which specifies pilot in command as the name in the pilot's name box.
Funny, I don't remember filing dual XC flights for my private under my
instructor's name either.

Either way, I'd have a hard time believing that the flight plan would
be the determinant information of who was PIC for a flight when more
than one pilot could serve as PIC.