You might consider then using Firestore and record simultaneously to P2 and to
Firestore hard drive and because Firstore records straight in Quick Time movie files,
you can pass the Firestore to client or your editor,
or you can easily copy those files to a computer,
so in all cases no need for editing software.
That should be covering 3 hrs 20 min (on Firestore), I believe as I never shot pn,
but I know when I shoot 720p25, 64 GB card records 1 hr but when Quick Time movies extracted through FCP are on my hard drive, it only takes 32 GB.
I believe that in pn mode redundant frames get extracted straight in the card.
Test it.