I had the same concern but I bought the SGP Steinheil EX Ultra Crystal Clear set that includes front x2 back x2 and the sides x 2 all for $25 which I thought was a good deal. I put the sides on last night and the bumper fits just fine over them, it does make it a little tighter so removal might need a little more force but it also makes it less likely to move around on the sides.
The point of the bumper is really to "fix" the antenna issue and not offer much protection at all. Dont even look at it if thats what your looking for, its a huge waste of $30!