If you are switching to shorty, you should also think about putting the ESC in the back of the battery tray and run inline. The person I bought my 4.2 from had used a toe block to mod in a little wall to separate the tray into two sections. I run a 1/2" foam in the front of the battery tray. Then I added 7grams to each of the rear triangles. The buggy felt GREAT with that setup. Alternately you could run the ESC shelf, but that raises the center of gravity slightly.