Which p-51 arf??? I would say it would be fine. The p-51 cowl is much smaller. I have a hanger 9 t-6. Had a gms 76 on it but thought the same thing you thought because of the huge fuselage radius and went with my old trusty enya 90 four stroke. perfect combo. Although I seen a review in I think model airplane news of the hanger 9 t-6.......................The author put an old webra 61 on his t-6 and apparently did just great. But I think these 60 warbids sound great with a four popper!!