Again, thanks for your help. I think I’ve resolved to run parallel. I have 4” conduit and flex between everything so I can fit paralleled conductors in one conduit. I’ll run 500’s from tap box to trans, paralleled 4/0 between trans and panel (because of the derateing of four single or eight paralleled conductors), and paralleled 3/0 again through the close nipple ( no derate necessary –less than 24”) connecting the tap lugs on the main panel to the main lugs on the second panel for the double tub 400 amp panels. Unless of course you have insight on something I can or need to do otherwise.
Thanks
Mic
