All cats get hot-- very hot; it's part of the catalytic process. While some of the high-flow cats sold for the Viper throw off less heat than a stocker, they also increase the sound level (which you may or may not want). On longer drives, the heat from any cat will start coming through the footwells. I keep the A/C fully directed at the lower outlets, especially with the convertible top down. Some here on this forum have experimented with thermal barrier sheets with good results, both under the carpet and under the car/above the exhaust.
I think this engine could benefit from a crossover pipe, but right behind the header collectors. Unfortunately, not enough room or ground clearance to really do this, at least not with a round section pipe! And the header collectors themselves are so far apart compared to most conventional V8 muscle cars, the effect of the crossover/balance tube would be diminished somewhat. Add in the extra heat and it's not worth the trouble.