I 've known these Veritron bastards for some time now. Very reliable but no toy, full of tricks. I understand your attempt to get him driving a bit smoother. Several posibilities here. But first make sure that the basics are OK. The RT 481 is giving an output in function of 2 inputs: the reference speed AND the tacho feedback. You may manipulate the speedreference. But I suggest to first check if your tacho feedback is correct. Imagine that the tacho it is not up to specs and giving a lower voltage than normal. That means then that your RT 481 will give a higher than needed output. Got it ? You can check it by trying to obtain full rpm,with little or no power, lets say 1000. If you are able to get more out of your drive, that confirms a wrong (to weak) tachosignal. Probably you never operate at 100% speed and thus didn't suspect the tachosignal. But remember the influence on your RT 481 output. That output will, further down the line, drive your current controller higher than needed.
Let's say: you checked the tacho's output all fine and up to specs. OK, then consider manipulating the speed reference. Do you have a reference value integrator ZD0022 installed ? That may sit on the RT 481. You'll find 2 potmeters on that integrator card. One for rate of increase, the other for rate of decrease. Adjust to your needs, but don't make it tooo sloooow. I did it once. My collegues, out here in the field, could not appreciate that.
At your service,