I was trying to come up with ideas the other day to get my numbers down when I remembered taping. I didn't have any of the tape so I took a big piece of Sam's Wrap and placed it under my nose and then halfway around my face then I put the mask on.
The seal worked great and it did keep me from mouth breathing. I only tried it for ten minutes and it did work so if anyone else wants to try it I would like to hear about it.
Yes, I know there are possible dangers to it but like using the tape they could be alleviated by rolling the ends or something.