we mustve been posting at the same time....

i'd say that a 40 might be ok for a 1/6th scale model flown scale like.

i had a saito 40 special in my kyosho 'stang that weighed about 2.7 kg and it flew very well.

also, the scale cowl didnt allow much more than the 54 i had in the eindekker anyway..perfect fit actually...who knows how anyone got a 60 or larger 4 stroke in there..

Tim.