To get an adjustable pivot bolt with lock nut similar to my R9s. Notice that I used a socket head cap screw to fabricate the new pivot bolt and lock nut (see the factory pivot bolt below the home made one and the cap screw used for the bolt). I also c-bored the near side receiver fork for supporting the lock washer. I also needed to inlet the stock around the new pivot bolt head and lock nut.
I also turned some brass pivot washers to replace the hokey plastic ones.
Anywhoo.........all these mods to the Quest (similar geometry as my Gamo 440) did help the accuracy some (30 yard accuracy improved from about 1 1/4" ctc to 1" ctc), but not enough to justify all the effort.