Why do you want a 4th half anyway - three should be enough for this run home. have a look at other positions for your price rang
My squad for the next two weeks would be pretty limited in options if I have to rely on Campbell in the halves.
That would mean bringing in a 2nd tier WFB to replace Campbell (Walsh on bye this eeek) my feeling is the second tier halves have a higher base than the 2nd tier wfbs so am preferring a Hynes or Galvin to a drinkwater or paps.