Well, you could hook up just one side to a SW21, and it would work for the transponders on that polarity. Your locals are on TP4 and TP9. TP4 is horizontal polarity, and TP9 is Vertical. Here is the breakdown:
TP4 - Horizontal
WCHS TV 8 (ABC) Huntington WCHS 7315
WOWK TV 13 (CBS)...