Everlast speed bag platform adjustment

[speedball708]

Is it better if you have your everlast adjustable platform to the highest setting all the way up or to the lowest setting all the way down? I have mine a little lower than in the middle with a 40 lb sandbag on top and it's pretty solid. But I would like a board solid as concrete without spending 100s of dollars. From what I've read even the expensive boards have to have weight on top to minimize the vibration.
Let me know what you think. Thanks