I don't know for sure what the runtime is like on the XX4... I never really paid attention but it seems that it would only charge back about 2500mah after a race? I promise I will check it next time so I know
If you don't already have a system, I would recomend the 6900kv for a small high bite track just because I think it would be more than you ever need. The 7700 is great but it runs hot when the track is super tacky.. but I have not messed with gearing much. I'm sure I could find a better gear. If the track is big I guess go for the 7700 and hang on.
There you go... short clip of the 8ight in action
The parts are homemade but I'm working on having some CNC motor mounts done as we speak. They should be pimp!... and I can get them for anyone who wants one.
I do know about runtime on the 8ight
at least for the track in the video above... believe it or not I get over 25 minutes on a 4s 5000mah pack!!!! That's right... runtime ranges from 170-230mah per minute depending on the motor/gearing combo I run.
I finished a 30 minute race including 2 minute warm up last week and it charged back 5448mah on my 8000mah pack.