Anyway, step one take the back half of the stock apart. once the yellow parts are off, you may screw them back together straight away, it's just to take them off their mounting point.
Cut the stock where shown either with a Dremel and cutting wheel, or your small hacksaw. I guess you could use a large chainsaw if you really wanted, but that's probably overkill and I definitely wouldn't suggest using an instrument meant for cutting down trees to mod your Nerf gun.
You need this piece that was originally forming part of the mount for the yellow pieces at the back to fit the section where the middle brace was, as the flat piece sticking out gives you some more area to glue to later on. to make it fit, though, you will need to file or Dremel down the two little tubes circled, as they're too big for the sockets in the stock. You can also use sand paper but that will take a while, but it can be done. Grind them down until they are gone, and also get rid of the little peg that the red arrow is pointing at.
Screw back together with the original back piece from the middle brace and your stock should look like the picture above (take note that the T piece sits on the inside). Glueing the yellow parts to the new shortened setup is fairly easy, just add some hot glue or epoxy to the spots pictured below (a bit messy, but you get the idea) and align the yellow stock pieces to fit.
Wait for it to dry and you're done! you now have a much shorter Spectre stock, which is probably a bit more practical for a "stealth" blaster. Hope you liked the guide, leave a comment or email pictures of your own ideas to cfb_rolley@hotmail.com if you've come up with a better way!