I will always keep the stock arm like you said. I know what you mean about selling it. It would not up the sale value very much or at all with the Trac arm. Better to sell the bike with the factory arm and get what I could out of the Trac arm.
I do not plan on running any classes with the bike. It is my wife's bike, but I do ride it now and then. So as far as lowering, you are saying I can get it lower with the Trac arm set at 0 versus the factory arm.
What class do they run stock wheel base in anyway.