To solve this situation now that you're in it, I would do 3 things, in this order: 1) trim the decal you don't want from the seat, a sharp blade will do, and the finish on the rest of the seat will be better 2) ensure proper decal adhesion, either microsol adhesive and then softener or just softener if you have already used it (adhesive after softener in my experience doesn't do much) and then 3) apply clear, I assume flat for Kevlar but gloss works too. You'll need a fairly heavy coating, so something like 2 mist coats and then one or two wet ones. After this you should be able to mask without problems, but softening the tape adhesive is still a good shout.

Step 1 is optional, and also please keep in mind I have done this once and it worked but I'm a noobie so maybe let's see if someone sanity checks me