I bet that shoulder stock could be adapted to the P17. Add an extended barrel to the P17 with that shoulder stock and it would be a fine little shooter.
Call me cheap but I would probably rather buy a pair of $30 P-17.
The p17 is the best bang for the buck no doubt, but these Zoraki's are multi pump and pack a punch for their size, especially the ultra version. I don't have one yet, but several guys here on the forum do and speak highly of them. Wyoman is one owner that comes to mind.
They come with a spare set of orings, the guns are built like tanks, They also come with a nice hard case, you get more than you pay for with these pre order sales for sure. Compare to a Hatsan jet or Notos and you do not need air supply.