I started flying my VVRC 20 about two minutes into the first tank. No need to ground run them any longer than it takes to put the initial tune on them. Don't run it rich, just be sure to have 32:1 gas/oil mix. 40:1 is OK after a gallon or two, but I run 32:1 in all of my gas engines and have never fouled a plug. I fly with the owner of VVRC, so I get good advice.