How often should you raise PF in a FR game?

[iggymcfly]

I feel comfortable playing pretty aggressively in 6-max and raising a lot of hands, but it seems like about half the time I raise PF playing FR, some short stack ends up limp-raising me and getting 70% of his stack in. How do you combat this?

Do you tend to only raise hands without aces or pairs? Only raise to 3xbb when you do raise? Only raise when there's 1 shortstack limper or less? Some combination? I'm already only raising in the last 3 positions, and my VPIP/PFR for 7 or more players is 27/10, but it seems like I'm not adjusting enough. The FR games tend to play pretty soft overall so I'd like to play them a little more, but the big pots preflop are killing me.