2003 F7 Standard. 75 miles on sled, 25 miles on belt. 160 pound driver, softest spring setting, coupler block on 1. 170 studs. 136 1.175 Woody's Traction Masters in the middle, 34 1.205 Chisel Tooth studs in the closed windows of 1" track. 1/2 mile glare ice. 50' roll out, then nail it. Fuel switch on ethonal mode 92 octane fuel in tank. Stock clutching 3600 engagement, 8060 shiftout. 1st run 112 mph. 2nd run 111 mph. D&D 3800 engage, 7820 shift. 1st run 111 mph. 2nd run 111 mph. Tighten secondary to 5th hole, RPM @ 7960. 1st run 111 mph. 2nd run 111 mph. Fuel switch to regular mode, down. Same D&D clutching, no changes made except to fuel switch. 1st run 113 mph. 2nd run 113 mph. Found belt going all the way to top of primary clutch. I believe this thing is out of gear in 1/2 mile glare ice. It won't go any faster. Gear sled way up to 24/39. 1st run 116 mph. 2nd run 115 mph. Shift rpm 7720. Belt 5/8" down on primary. Made changes to weights, springs, and helix. Don't think it will pull this gearing on the big end. 23/40 is probably the way to go like BYOFFCR has said. D&D clutching pulls hard at bottom and midrange. Should work well on trails for corner to corner bursts and short drags under 1/2 mile. Would like to see more rpm. They pull the motor for acceleration. It does that well!