I found on my setup that the top end was worse. 6th is incredibly short so you knock it into 6th and it gives you a tiny bit more top end.
But I'm running ridiculously small rear wheel/sprockets since that is all I can find. Probably closer to a TZR actually. To be fair I spent a ridiculous amount tuning that 4DL, porting, Ignition, carbs and it was very flat, very slow. Now I don't know what I'm doing wrong. Must be something but the 4DL 3MB00P was nothing special.
I'm not knocking you, you got yourself a bloody bargain there. Just saying my experiences. If yours differ please let me know.