Not quite a mountain biking question as much as a question about a mountain bike:
I use my Giant Boulder (formerly SE, before a swap for a rigid fork) purely for commuting around the city. Often I'll meet my girlfriend somewhere she hasn't brought her bike and I'll end up doubling her on mine. I was just wondering about the feasibility of rear pegs, so she won't have to balance precariously on the seat while her feet dangle. Is it absurd to expect the axle to deal with 280lbs. for ten or fifteen minutes at a time a few times a week?
Are there any risks (to the bike) I haven't thought of?