D8R-sorry to hear that. This model is way to nice to give up on
I can say this is one of the problems of almost finishing a model without checking all systems but you probably don't need or want to hear that
. I no nothing about hyds. but I was not aware that it took a strong servo to hold valves on center. Could it be the quality of servo that you are using? I say just give it a few days and then slowly work out each problem. You have built a great model and I am sure you can figure this out.