Personally, I don't think the stock chassis needs replacing at all to be competitive. It needs the lightest electronics though, and a lipo pack under 230grams with a spool up front(with losi LCD's losa3344), Acer Bearings, lightweight body, parma wide bumper....... Once you can get it balanced , tweak free, and under 1380grams, you will be competitive..... I run mine at 1471grams in 17.5blinky, and it's very competitive eventhough it's unbalanced, tweaked, and I need alot of practice.... The hardest part is to get it to go straight with my analog servo, and that loose steering bellcrank.....