GP DR1 & Saito .80 eng.
I have a saito FA80, usually run a 12-8 or 13-6 but it will easily haul a 14-5 or 14-6 prop, even try a 15-6, no kidding! I run a 15-8 on my OS.91 FS and it loves it. Four strokes dont mind lugging extra prop as a 2S does (and will overheat). The plane is draggy and you dont want a high pitch prop, go for a lower pitch, larger diameter. I'd try the 13-6 or 14-6.
AJC