X-15 is a good disc, slightly overstable, decent glide.
Honestly there are some decent flyers in te Lightning line, if they had kept up with the trends like premium plastic and high speed drivers we might still be trowing them.
The stamps and marketing weren't great either, if I were running an emerging company, if make a few calls and see if they would sell the molds for the u-2, the hookshot series and the helix series. Take away the weird rim grooves and give it a killer stamp.
The U-2 is a vastly underrated disc. If you could get it in a Star or Tourment plastic a ton of people would have a new driving putter.