Brian, sorry not to respond to this sooner. You are on the right track in rewriting the plan files with the desired geometry and flow files. However, for RAS to automatically bring those geometry/flow files in, without manually importing them, you have to also write those geometry and flow files to the project (.prj) text file. Here’s an example of a project file with multiple plans and multiple geometry and flow files:
Proj Title=Bald Eagle Creek Example Dam Break Study
Current Plan=p13
Default Exp/Contr=0.3,0.1
English Units
Geom File=g06
Geom File=g08
Geom File=g10
Geom File=g11
Geom File=g12
Geom File=g09
Geom File=g13
Unsteady File=u07
Unsteady File=u08
Unsteady File=u09
Unsteady File=u10
Unsteady File=u11
Unsteady File=u12
Unsteady File=u13
Unsteady File=u01
Plan File=p13
Plan File=p15
Plan File=p17
Plan File=p18
Plan File=p19
Plan File=p03
Plan File=p04
Y Axis Title=Elevation
X Axis Title(PF)=Main Channel Distance
X Axis Title(XS)=Station
DSS Caption Additional Text=PMF Inflow Hydrograph