The area you drill on the inlet side pretty much looks the same. Only thing it is inset in a ways requiring the use of a long drill bit. When you have the muffler off you will understand. Lots of empty space before the baffle you will be drilling.
Is only 4 bolts to take the muffler off and see for yourself. Take off,peek,and then decide whether you want to spend the $10-15 on a drill bit. Lots are happy with just doing the outlet side.
I have both side done with no complaints. It doesn't annoy the neighbors,but is heard.
*Note-- Also done the marble mod. Block off plates are cheap,but since I wasn't worried about weigh it seemed pointless to install some where the marble yields the same Desired effect.
Have fun and good luck!