Phil,

A real easy starting point is a 2.5mm restrictor in the C port (compressor), nothing in the W port (actuator) and nothing in the R port (vent to atmosphere). Using a -31 installed with half hole preload will normally give around 1.6bar held on a T38. To up this shorten the actuator rod one turn at a time until you get your desired boost. I found I ended up with one full hole preload and above jetting to get 1.9 bar held on last T38 car I mapped.