Good correction work on an impressive looking car there mate.
Personally, I too would have stepped to using OP on a polishing pad to see if that cleared up the marring or stepped to a lighter abrasive than OP - something like #80 as Scottwax suggests or something like Menzerna Final Finish.
Personally, I dont really use the PC anymore for any defect correction, all the work I do is by rotary as I personally feel I get better, more crytsal clear results from the rotary, especially on solid dark colours... Just my personal feeling though. If you feel like trading up to the rotart, get yourself some scrap panels to practice with to hone your finishing techniques, as once you have mastered finishing with the rotary, the PC will stay in its box.