"EXHAUST DRONE"

i understand the droning theory of frequencies causing noise and the fixes of adding tee off back of muffler kind of like the water hammer bumpers on water pipes in your house. it works but before i go cut up new exhaust has anyone heard of putting in softer rubber mounts on hangers to give a little more to maybe change freq a little. all mine are solid rubber and 4 of them just on muffler. i was thinking of unhooking two opposite corners and then maybe drilling a hole in middle of other two to make flex a little.am i nuts or does this not seem to be a way to change freq?i might also add weight on tailpipe. i know these are probably the first things to try before hacking ,but was curious if anybody has tried and had positive results