I had 3 of them at one time (back in '99-'02), very fun cars! I used a "stockified" motor in mine, it was a 18x2 arm in a P2K can with bearings. Had all the power I needed for racing it the way I did.
When set up properly they are a very capable jumping car too. They don't particularly like real loose dirt or rough tracks because of ground clearance. But on a hard pack clay track they really shine!
The one thing I found they needed (with the advice of other's online) was a upper deck replacement, one where you can put two more stand offs in front of the battery. I helped stiffen the car and make it even better. Problem is, even when I ran mine, HPI did not make the upper plate anymore. I got lucky and found one & then used it as a pattern to make a few more out of carbon sheet.