Don't add another regulator. Each regulator adds a bit of restriction in the air flow, so you want to use the miniumum number of regulators that gets the job done.
Remove another shim and try that first. By increasing the spacing between the open on-off closed position and the sear catching the bolt, you reduce the reactive effect. The ULT was designed to reduce the trigger pull and the reactivity of the valve. We have overridden that and used the ULT to give us more reactivity by adding extra shims to reduce the timing between the on-off closing point and the bolt catch. Removing the extra shims will put the ULT operation back where it was designed to operate.
Except for the Automag in front, its usually the man behind the equipment that counts.