If in fact Bisping has a 70% chance to win then the line should be -233. So yeah, -170 would be low in that case. But I could always be wrong and Stann could show us just how wrong I am when he blows Bisping to pieces in 30 seconds. We both know how this sport is.
BTW, if you ever want to know what the proper line is for any given percentage, this thing is pretty handy:
http://www.covers.com/sportsbetting/money_lines.aspx
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