Not familiar with Tamiya Tape. Our masking is a special light adhesive coated paper with a release liner. You can print on the mask side easily and cut with an Exacto knife or similar tool. We sell our masking paper in 8" x 10" size sheets in 3 packs ( $ 4.95) and 10 packs ( $ 12.95).
Never thought of darkening the edges of the Gator masks with a pencil and then scan the sheet. Now that is why I asked for help on this project.
Well that will work too, its the same sort of material that I use Tamiya tape is "Washi" tape, generally known as Kabuki tape but its proper name is "Washi". Tamiya's tape is expensive but you can buy much larger rolls of it on household painting sites as painters tape, but search "Washi" tape to find the right stuff, I use "Kip" tape. It is the most useful tape for none pre-cut masking
And yep, asking usually gets a result Rather than using a pencil, produce graphite dust, by rubbing the pencil on emery paper and apply the dust over the masking sheet before weeding it. That way you will save getting the dust on the backing paper which will blur the line.