center shock
I was able to replace the center shock with one from a Losi JRX-S. I replaced the rod end with a Losi JRX-S sway bar rod end which fit on the stock AE upper ball. Cut the rod end slightly to set droop. Replaced the center shock front mount screw with a 4-40 which doesn't have any play once tightened. It felt a lot better than the stock one which was starting to feel gritty. I was expecting the stock one to last longer due to the two plastic shaft bearing.
I can run stiffer springs. The 30 lb/in spring seemed to work well.