Marshon gave some good info on making the decision. The other factor specifically at the nats was the elevation. The track was at an elevation of 6000 feet! So really high, to make power everyone was running 40% nitro and I've heard that some were ever running 50%! We ran 40% with an 8.5mm reducer, so this is a way different set up than what we would normally run anywhere else or frankly probably ever again! If you look at the video you will notice that some guys were pitting at 7:30-8:00 and you can hear the announcer mentioning 1 or 2 of them flaming out as they come into the pits lol. The set ups that everyone had to use at this track was simply not conducive to long run times but even at that we were getting 9 minutes which is quite good!