I like ESPN's performance league positions:
(Ideal for 12 or 14 team leagues)
Thus, a team has an option of going 1 RB & 3 WRs OR 2 RB & 2WR depending on matchup..
any option of starting 3 RB's is overkill as generally you'll want to start 3 RB's every week.
The key to Fantasy Sports is NOT about Sports but rather the "manipulation of numbers" in your favor
MASTER THOSE NUMBERS