I'm trying to determine why are you still talking about running four conductors? its a 1-phase, 240V so you are only running three conductors (2 hots and a grounded neutral line imbalance) so conduit derating shouldn't apply during this.
voltage drop calcs will require the load information. now I'm guessing, but with a 200A main, i'm assuming 160A max load (main sized at 25%), unless you have additional loading that will make it higher. my calcs say 250MCM is more than fine, but as mentioned in previoust posts, 4/0 can work just as well.
are you using schedule 80 PVC? 2" should meet the conduit fill requirement per code, using 250MCM. schedule 40, 1-1/2".
voltage drop calcs will require the load information. now I'm guessing, but with a 200A main, i'm assuming 160A max load (main sized at 25%), unless you have additional loading that will make it higher. my calcs say 250MCM is more than fine, but as mentioned in previoust posts, 4/0 can work just as well.
are you using schedule 80 PVC? 2" should meet the conduit fill requirement per code, using 250MCM. schedule 40, 1-1/2".