You can place the necessary resistance between the rectifier and first cap, yes, and that is probably the easiest in practice and to simulate in PSUD2. Or you can put a resistor in series with each plate between the secondary winding and the rectifier. If you want to model it that way in PSUD2, you have to measure the DC resistance of each half of the secondary of the power transformer and add the needed resistor value when entering the data into the program. If, for example, your power tx has 50 ohms DC R in each half of the winding and the rectifier needs to see 100 ohms per plate, then you can simply put a 50 ohm resistor between the rectifier and cap, OR you can put a 50 ohm resistor in series with each plate between it and the secondary winding of the PT. They are electrically equivalent. Whether one way sounds better than the other...? Try it both ways...