Was thinking about getting a Slow Stik and wondered what some good mods would be to make a good airplane even better.

ColonelG mentioned the mods that I would recommend, but I'll add the following:

1 - Use two servos for the ailerons, one on each side.  The first one I built with ailerons, I used one central servo with torque rods.  Using two small/lightweight servos is much easier to set up and the direct pushrod won't have as much play in it.

2 - For the aileron servos, cut the mounting tabs off and wrap them in heatshrink.  Make sure the heatshrink wraps around the corners.  This allows you to glue the servo to the bottom of the wing without getting glue in the servo.  Also, if/when you need to replace/repair the servo, you simply cut the heatshrink open, repair the servo, reinstall and close the heatshrink up and tape it closed.

3 - When you cut the ailerons, go all the way to the wingtip with the aileron.  My first one only used the aileron "cutouts" and they weren't nearly as effective as going all the way to the wingtip.

Hope this helps...
Chuck