I raced a xxx-4 (with good results for about a year) both outdoors and indoors. I strongly suggest the A-main racing Aluminum hub carriers, as the stock plastic part breaks very easily. I had the G+ edition which I also suggest, as the graphite parts seemed stronger. As for motors, I normally used a Velociti 6.5R and in extreme cases, ran the 5.5R. I basically locked my slipper down and loctited to keep it from backing off.
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