I cut my proscar into 5th, I was worried about sides at first, but honestly I think many people on here don't realize the impact your mind can have on your physical state. I take my proscar everyday and don't spend much time at all on these message boards, just live my life, and that would be my advice to you. My current doctor, and my surgeon (I had my appendix out) both take proscar cut up, so probably the 2 smartest people I know in medicine take it, I wouldn't worry too much.
I personally would advise taking 1mg, just because the hair loss remedies take soo damn long to work. If you take only .25mg you might waste a whole year, since I found it took close to a year before I started to actually notice any results.