Had Enough

My lab group has really pissed me off by now - this is the second lab report I'm doing all by my lonesome. They're getting what is probably the worst sort of peer evaluation possible from me: a truthful one.
Exhibit A: Doesn't come to lab, worked on lab report 1 and 2, no effort for the rest.
Exhibit B: Total work done to date is as occassional lab assistant and, well, I guess he did print a few pages for me when I was out of ink...
Exhibit C: Wrote a program our GSI would have given us anyway. (and that's all folks!)

I'm wondering if it'd be better if they got a C grade, and thus the worst possible blemish on their GPAs, or a simple fail so they'll be forced to repeat the course. Who knows... I think my intention of general nastiness and mayhem is best served by Fs all around, though, because then they'd be forced to repeat the course - and its not like an F dissappears off your transcript (unless you have a valid reason - and "I'm lazy" isn't valid), though it won't slash their GPAs.

Am I being petty? Possibly. But its a position that I'm perfectly justified to take under the letter and spirit of the school's academic policy.