Actually, at lower limits your check-raise% shouldn't be more than 1%, because value betting renders more profit. I read this from a 2+2 post, and it resembles mostly my style.
11. Check-raising. Some people never check-raise; others check-raise infrequently. I personally like to check-raise at least once in awhile; 1% would be fine, 0.5% would be acceptable. The goal of the check-raise is to remind your opponents that just because you checked does NOT mean that you don’t have a hand. However, circumstances need to be very specific for a check-raise to be appropriate. Typically, I check-raise on the flop when OOP against a preflop raiser, or on the turn when OOP against a flop bettor/raiser who was clearly not on a draw (uncoordinated flop). If you are check raising much more than 2% of the time, you’re being entirely too tricky for a SSNL table, and straightforward play would probably be more profitable for you.
http://forumserver.twoplustwo.com/showflat.php?Cat=0&Number=4946669&an=0&page=0#Post4946669
I don't know about Fixed limit, but I think it's basically the same?