Correct, the plane will not fly at that speed, you have to adjust rpm and manifold pressure to remain at a constant speed. the dot speed command is for climbing at a certain speed, for example, the P38 climbs awesome on speed 255, and the F4U on speed 225. The reason I set these is so that I can climb at a decent rate while getting to my target in a reasonable amount of time. Also, if you encounter a con you have some manuevering speed. Just a suggestion.
Jason