The trick hear is to be sure and drill enough holes in the walls so that you get an even and uniform amount of insulation in the walls and that it is not packed to tightly. Often while on a job I drill a hole at the very top and then drop a 'plumb' line down the hoe to see where the next stop is. Go about 16" below that point and drill your next hole. Keep in mind that your holes should not be more then 8' apart no matter where the stops are located. Be sure to do this for every run since some runs will not have any stops and some runs will have 4 or 5.