I'm not familiar with FSC9, but if Markoz recommends it I'm sure it's a good solution. I haven't flown the B-52 for awhile, so I'm not sure if the control is in Tacan, I think so because I do leave the selector in the same postion for the entire flight.  I flight plan from airport of origin to an airport near origin, and then click and drag the purple course line to a destination/turn around point, and then back to the airport that is my real destination (as the second to last checkpoint) and ignore the leg to the final flight plan airport. I have not added GPS but I did add the Carousel INS and use that sometimes in lieu of flight plans to set Lat-Long coordinates as checkpoints anywhere in the world and then the Buff flies the INS legs.