I am a heavy mouth breather so wanted to share my mouth taping experience. Chin straps don't work for me (they slide off, jaw hurts, still have air coming out lips, etc). So taping was my only option, IMO. But the puffed cheeks and the drool (have since figured out my high pressure (20/16) forces the saliva from my mouth when I open it causing horrible dry mouth) frustrated me as my tape would loosen from the moisture.
While browsing Rested Gal's links (YOU ARE THE BEST!), I ran across a post where she explained how the jaw relaxes and moves back when you sleep, hence the need for chin straps. So that led me to try an extra piece of tape under my chin. This piece I make longer than the mouth tape and actually place it so the ends overlap the mouth tape.. This stops the blow fish cheeks and the chin dropping back. Don't know if it will work for anyone else but it has worked for me beautifully.