That would first depend on how Satisfied you were with the current set up numbers, then pay attention if the driver has a growth spurt especially in upper body position while in the seat, If the drivers head is higher and more upper body mass you'll need to lower the rear of the seat ( again provided current set up is good ), then adjusting for the added speed and force it puts on the chassis, Go off numbers but provided you were happy with current set up numbers, I would add around 1 % left, and 2 % cross UNLESS your on high left and cross set up now. I would question 50 lb more needed from Jr 1 to Jr 2 as it's usually not that much difference.