FEJ are saying that the F18 should weigh around 30lbs,so with full fuel load that makes about 35/36lbs.If an engine of that thrust is used we would still have around 1 to1 thrust to weight ratio is that not enough!!Big engines are more weight use more fuel which means less time in the air,It is a fact that light planes fly better than heavy ones,i have just finnished a Tri-star which with fuel is 30lb,with a Wren super sport for power [18lbs thrust] fly,s great,climbout is at 45degrees and will cruise at under half throttle!just a few thoughts in the end we all do what we want regards KeithW