I haven't played GHS nylons, but my understanding is that they're the only tapewounds where the core is an actual flatwound, as opposed to a roundwound on La Bella, D'Addario etc. I'd presume that the new string would sound quite differently from the rest of the set. Whether that would yield a good or a bad result I have no idea.
My $0.02 only...
Good luck.
This may not be worth much, but I just installed La Bella tapes on my Mod Shop Jazz. They appear to me to be flats. I can't be sure but they are quite smooth and at a close look they look like their winding is flat. I have Fender tapes on a fretless Jazz and they are quite obvious round wound beneath the tape. The LaBellas are still new and I don't know how they will sound in a month or 2 but right now they are fairly zingy for tapes.
Tim