I've got a new bike which has a hollwtech II 105 crankset. I need to change the rings on it, but the manual is VERY specific that the two left crankarm bolts be tightened to exact specs to insure the crankarm doesn't fall off. I've exchanged older square-taper stuff within minutes, but this is definately different, since the spider arm has no bolt at all.

How important is getting the torque correct?