What surface are you going to be running on?
There's not really much needed you need to do to make the car stronger/faster, it's bang on straight from the box
There's one little tweak to make the slipper a little more reliable. Put an extra washer on the screw head end of the slipper bolt and screw one of the tiny screws that normally capture the hingepins into the other end of the slipper T-nut to lock the slipper setting in place.