My personal preference is Biondo Elite 500 box with a dedenbear under the carb electric stop that has the primary kit. This setup works good whether you are killing a few tenths or a couple seconds to get to a 90.
a linkage stop will work, but is nowhere near as consistent. Look around at the winners and you generally wont see a linkage deal.
The starting line enhancer is awesome when bracket racing a fast car, but its no use on pro tree racing.