The fittings on my MD-20RZ are 11/16", my Weapon HC will have 5/8" Fittings, everything else is 1/2", so really the only place I can use bigger tubing is from the pump to the radiator, I'm thinking Tygon 5/8" ID 15/16" OD, then 1/2" ID 3/4" OD for everything else, sound good?