bender-freak is right.
The modern six-saddle bridge is good for P/G or P/W benders, if the bent string saddle is open at the bender end, as in the Standard Nashville B-Bender. See photo - counting from the bottom: Standard modern saddle, factory made bent-string saddle (open), home-customized half-open saddle for the same experiment you did:
Larger pic:
[img=http://img217.imagevenue.com/loc194/th_60540_Saddles_122_194lo.jpg]
The pressure of the string on the saddle is fine for the built-in P/G, but not for the Hipshot. It killed the sound of my g-string, so I removed it again.
Mysteriously the same experiment was successful on another guitar, equipped with a vintage three brass-saddles bridge. I had to make a notch into the before unnotched saddle, otherwise the string traveled when I finger-bent it.
Now for the best part: Just for experiment I built in a cheapo no-name bridge with three pre-notched chromed steel saddles the next time I was about to change strings, and that improved the already alright sound of that guitar by at least 100 percent. In my case the cheapest and most simple solution was the best:
Great working ashtray construction with simple saddles (Shelton B-bender plus HipShot G- and D-bender)
I just ordered another 10 bucks three-saddle-bridge to finally equip the above shown Nashville with the multi-bender.
BTW: Will Ray sez it's better to drill holes ***very*** close to the top edge of the bridges end than make notches there, as this generates a little more pressure on the saddle without generating too much friction (the same what your retainer does). I haven't tried that yet, as you also see on the photo, but will try it when my new bridge arrives. Crucial is to use a little bit of vaseline or Big Bend's Nut Sauce on all possibly friction-causing contact points of the string (bridge holes - if there are any, retainer - if there is any, saddle, nut, tree).
Greetings and good luck with optimizing your bender!
Luther
Edit: BTW if it's alright with you to use heavier strings, use at least 10s, better 11s. Best 12s or 13s. Doing all this I think you can lower the action again without shimming the neck.