Shocker SFTs and Nerves share the same board with the Shocker NXT. The only programming difference of mention is the beam-break eye system. SP boards programmed as of August 2006 will work in both markers. Previous boards will only work in SFT markers (or Nerves).
Older aftermarket boards can be reprogrammed to function with the NXT eye system, however you will have to send the board back to the developer for the reflash.Even though SFT/NXT boards use the same hardware, only boards with trigger microswitch installed in the "flipped" position will work in a Shocker NXT (flipped position is shown in the picture higher up on the page). If the board has a non-flipped switch, it won't work.