Weight alone doesn't dictate speed because it's internal.
ehm... nope
If youre flying a 262 at 220mph, the nose will point up about 5-8 degrees, if youre flying at 500mph+, the nose will point down 1-2 degrees (in level flight of course).
Why?
In straight level flight the sum of al the forces taking effect on the plane is zero, right? (straight movement without any acceleration)
What are the forces attacking the aircraft? There is the gravity, the thrust, the drag and the lift.
Lets see the lift first. Its about the air pressure differences over and under the wings, what also comes from two components. The first one is from the wings aerodinamic profile what can counter the gravity if the plane goes totally straight, its nose isnt pointing up or down. The second component is from the airflows angle of attack.If its zero degrees, the it has minimal effect on the drag, but even if its 4-5 degrees, the drag will increase dramatically causing the plane to slow down, while the lift is increasing.
Summa summarum if you have a light aircraft, you dont need to use this second component, the plane will be able to go fast. If your aircraft is heavy (even if its all internal), the lift will have to counter the gravity force coused by the extra weight, and the only way is to convert the drag to lift, the plane will be slower.
I hope it was understandable.
Btw the b29 is pretty DANG fast. With wep it can do 393 at 30k. Last time i tryed it, i got 4 (!!) 163s without losing a drone. I am a horrible shot and very rarely fly bombers, but they couldnt jump on me as fast as they wanted and were easy kills. Not sure about this bomber being correct.