The JRXS-R has only one real problem in its chassis configuration, as nearly all touring car racing is now rubber-tire the prevailing opinion of designers is to longer A-arms, moving the mount point of the arm closer and closer to the center of the chassis. This (in theory) helps with the lower traction you get out of rubber tires, as when running softer springs the chassis can roll and dive more without changing the angle of the tire relative to the track. The stock springs on a Type-R are 30lb/inch in the front, 17 in the rear for foam tire racing. In running rubber tire, I run less than half of that to get dive and weight transfer.
Also, nobody makes gear diffs for the car, so its ball, spool, or nothin.
Aside from that, Shorty Lipo's are your friend, as they let you mount your receiver and ESC behind the battery, so its a straight in-line car.