Well, I decided to use the Flex today since I was told that the red bp would be okay to use while I waited for the black one. I have to say, I LOVE IT! I was able to do some polishing and walk away with out back problems. Very nice. I didn't think that I would use speed 6 cause when I turned it on inside it was very loud and fast, but after messing with it I was all over 6. The machine isn't that loud outside, inside its very loud. Vibration was NOT an issue at all. With the PC I would polish the roof of a car and my hands would feel the after shock of the vibration for a long time, not at all with the Flex. I was able to put pressure on the machine and it did not bog down one bit. I have to say that I am very happy with this machine, and thanks to all who have written reviews about it and led me to spend money 
