I assume that teams reduce their rotations down to 3 or 4 once the playoffs start, am I right?  My question is even though your #3 guy hasnt performed as well as your #5 guy throughout the season, do you still go with him in the shortened rotation?  We are still a good 90 games out in my league so its really a moot point right now, but my #5 has been better then both my 3 and 4 guys but ratings wise, he isnt the same caliber guy.

That's just a ratings vs. results question.    You could be misreading the ratings.  Or he could  be outperforming his ratings.  At the end of the season, I'll usually go with the results but give him a quick hook so my ratings guys can get in as a long reliever(also on a short leash).

I agree.  I go with the guys that performed the best.  Just recently I had a #5 SP that went 15-3 in the regular season as my #2 in the playoffs.

As far as how many man rotation, I go with the amount of SPs I can trust with a playoff start.  If I feel I only have 3 good SPs I try to go with 3 if I can get them back to 100% in time.  If I have 5, I go with 5.  Try to get my ace start the 7th game if I can.