Back flow devices in series/Critical Analysis

Lately, I'm seeing projects where the irrigation POC is downstream of a large back flow device, usually a building-wide RPBA. The irrigation system is further isolated from there, usually with a DCVA. The CA, after sizing the main line, only accounts for the first BF after the meter. I know I can add the second manually to the CA, but is there any way to make it account for both? I have to delete the first to see what loss is through the second one and then do the math. Or is there a work-around?

Thanks!