In another thread, the one related to ram solenoids, there is a website that sells pneumatic valves. After extensive discussion with their people, I've found that these valves are suitable for our applications (both retract and brakes). The cost is something like $25.00 for a brake valve (fully proportional) and $25.00 for a retract valve (fully proportional or on off/ for robart or spring air).

I wouldn't all jump ship and start making the calls yet, I'm ordering some for testing in my kangaroo. Should have all operational in a couple of weeks and I'll post my results on RCU.