I just got some 17/40-16.5 Grand Prix 4-Wheeler RTV tires and I was considering altering the center tread pattern to open them up more. I have a picture showing the tire tread now on the left and two possible other patterns to the right. The pic is at http://community.webshots.com/user/aalundberg and is the 1st photo under the tire/wheels album. Anyone think one pattern is better than the other, or should I just leave them alone? I can get them cut out for about $15 per tire. They'll be used mainly for mud. Some pavement use on occasion.