reworking a fully restored car

No this is a different douche bag . I am getting a lot of help with this so I am sure it will be right when it is done , I don't weld but am buying a spot welder for the body panels and a great fellow FABO guy is taking care if the tig welding on the frame and the patch for me . Question for all you welders out there what effect does changing the copper tongs on a spot welder have on the unit ? I want to trade the 6 inch ones that come with the 110 volt unit to a pair of 18 inch ones from Miller , will this affect the thickness the unit can weld or just the duty cycle or will the increased copper overload the unit all together ?