Some people have been saying the stock springs are to short/soft.
I use the O rings in the front and centre diff but not the rear like the instructions said. And run 5,000 in the front 3,000 in the centre and 1,000 in the rear.

It's a full out racing buggy it doesn't need any mods apart from a zip tie on the fuel cap. Although i have seen somewhere that someone put a three brake disks on instead of two.