Some of the Saginaw boxes are "variable ratio", with a very fast response just off the center point, then a slowdown of steering response for parking, etc. near the ends of the steering gear travel. This is done with a taller center tooth on the sector gear in the steering box. If you can find a constant-ratio steering box instead of a variable one, you'll probably solve your problem without having to tinker with pressure or fluid flow.
Jerry
