My 6 year old son just started racing with a 79cc preditor engine... we have a 2015 ultramax big pipe chassis. The weight rule is #225 ... Cart and driver are a combined weight of #265 l, 40lbs over weight. No lead in kart, asphalt oval, son is 55lbs, trying to make plans for next year and want to be closer to the weight limit. 40lbs is a lot of extra weigh! Thinking of getting small tube chassis and was wondering the weight difference between big pipe and small pipe chassis. Kart also has rocker cage on it..