Hi Hollyclay, Bummer about the running Red.Two things come to mind, neither have I ever tried. One would be to prepare the surface of your cured PC before you apply the marker by cleaning off any surface oils with alcohol.
Spraying a very light mist of PYMII over the dried marker in several very light coats, drying in between might also be a possibility
I'm looking forward to reading replies to your post because I need to find a thin tip permanent red marker that will work on PC, something I've never tried before. What brand of PC are you using? Do you remember the brands of permanent marker you've already tried over the years? That would be helpful for me to know so I'll know which brands NOT to try.
Anita in AZ