Thhe size of UR header tank is not very important! In fact, the smaller the better. 1 Oz size is sufficient.
I make a holder from thin sheet aluminum about 1 to 2 inches wide. Just shape it in a round shape to fit slighhtly undersize of the tank diameter. Allow an extra half inch more each side & drill a hole for a self-tapping screw to hold it in place slightly ABove the Carb needle valve. Too large a header tank only encourages foaming which U R trying to avoid!!!
The tank should be snugly held in p[lace...so drill the screw hole in the right place to achieve this.
Dr. Gravity.