You can run the JP-1 but you are gona get horrible fuel mileage. I would personally run the 2045 pipe with a 198 header. In the Losi the stock gearing is 13/48 and I always changed it to 13/50 when running the WS7. I tried 12/48 but that was too drastic and killed my top end too much so you may want to consider 2 teeth bigger on your spur. As for the clutch, yes you are right the WS7 likes a heavier clutch as it does not have the big torque to get the car rolling initally, heavy clutch springs do help this but I always preferred running the standard clutch with the gearing change to help the engine get in it's ideal power band sooner.