By the time you go out and buy mouse mat pads, adhesive, and double faced tape, you could have just bought a kit and got the job done. Not to mention the time to sit there and cut thin strips, then cut strips of double faced tape to adhere it. Jon Goodman sells the seals for the RB67 in 3 kits. 1 for the mirror damper $6, 1 for the rotating back $6, and 1 for the film back $10. Ask yourself, for $22 would i want to sit there and cut mouse mat and double faced tape, run to the auto parts store for adhesive? Or buy a kit with complete instructions, pre-cut seals and adhesive already applied to the seals where it needs to be? Using mouse mat to "patch" up a small light leak where a light seal was torn may be OK, but i wouldn't want to do a whole camera with the stuff.