It will be difficult to model in Caesar an antivibration support. Actually these supports have some disk springs that need to be tighten, not by hand but by wrench. This way it will not allow for vibration in vertical plan and in less amount also in the horizontal plan. It will create a grip that oppose the movement and also vibration. The Pulsation study can estimate the dynamic forces that appear at the location. If friction is bigger that the dynamic force then ok, if not then you have to place a real restraint. So this will be an iterative process. And you do not have very much control on this. The only thing you can do is to physically place rigid restraints at smaller distance in order to achieve the desired frequency. The best solution is to give the task to the manufacturer as they have all the means to solve the problem.
You can try to see if applying a force downward at the support location it will increase the frequency. I think that on your Supports Standard the value of torque should be specified.