Hoping i could get some advice on a double sided stove install. Need to finish off using either supalux/promafour from what I can gather. One side is a 4m wide wall so dont want to use expensive board all along this stretch. Can I use pink fireboard once far enough from the fire? Should i use vitcas plaster in the vicinity of the fire then multifinish? Can i blend the vitcas and multifinish without a visible join?