I've had Exocet Cross 90l/59cm from 2006 and Cross 94l/61cm from 2016, double rear footstraps, flat water blasting and B&J. I'd say very similar sort of boards to your JP board.
For the Cross 90 I used 5.6m & 6.5m Naish Redline 3 cam freerace, 6m Ezzy Cheetah, 5.2m Ezzy Tiger and 4.5m Ezzy Panther, plus assorted older Ezzy wave sails. On the Cross 94 I used Ezzy Lion 6.5m 2 cam instead of the Naish sails.
I've used loads of fins over the years. If I was going to buy now, I would get a Select Edge 29cm, Black Project G10 Kracken or Freewave 24cm & 26cm (if they still make them), or K4 FSW 24cm & 26cm for cheaper plastic fin. Or if you just want 1 smaller fin, a 25cm Select FX Freecarve.
Or any which look like these. Maybe not the upright Select 25cm slalom fin, it was only good on flat water & higher winds.