Safety is the biggest thing. I don't think they worry about the 6x6's for much of anything other than safety because it is so small, unless someone complains.
just happy we are back on the track, most racers are built with machines from that era and the rules worked before. there are rules posted on needt's web sight for the six wheelers.its not like someone is getting payed to set all this up. and the rules were updated some.