On beers (my last comment). In the past if we wanted to get our american / canadian cousins absolutely off their collective faces we would feed them in increasing order of "strengths" Coopers (SA) Resches or Tooheys (NSW) Fosters or
VB (Vic) and finally XXXX (not the condom) from QLD or Bulimba (sadly no longer available). If in the NT we would feed them NT Draught. Usually 3 or 4 XXXX's would see them off their faces. HOWEVER it was totally the other way if spirits were involved, fortunaly I learnt Vodka lime and Tonic tasted the same as Lime and tonic.
Now Hobbsy a 13.5 x 8 should go well on your 80. What sort of prop and I am assuming you are using something like 15% nitro. The type (material used), and construction (blade design) have a lot to do with the performance. I have just been shown a 13 x 8 wood that when measured when it came of the a/c was in fact a 13 x5 due to hub compression. I am getting ready to go out to play and I am using 2 different design props on Ivrine powered bombers (same size).