If you pay back the PD to WC and collect SDI, then when the case is over you will have to repay SDI so I'm not sure you've gained anything.
You can only collect SDI if there is a doctor signing off that you are for that period of time disabled and unable to work. If you were totally disabled, why where you receiving PD? If you were permanently partially disabled, why would a doctor be saying you were temporarily totally disabled? Lots of questions. Maybe it's time you sat down with a lawyer to go over all of this..
You cannot game the system. If the Insurance owes you PD and EDD paid you for the same period, EDD is going to get the money from your settlement. If there is a doctor who states that you are TTD, EDD will pay the difference between PD/TD until it is resolved. However, you really want an Attorney to assist you before you start juggling knives like that.
We offer general concepts, but you should give ALL your facts to a licensed Attorney in your state before you RELY upon any legal advice.