You can try the B-Tech BT77's. I know that you have voiced issues with the depth of the RTi6's, but I think it depends on how far you want to tilt the speakers.
Since I have my RTi4's inverted (upside down), I have black zip ties fastened to the hole in the BT77 base to the keyhole on the Power Port. Having them upside down makes for a very short zip tie run. (BTW, I have them upside down so the tweeters are mor in line with the center channel).
The other option is to use the screws that are included with the B-Tech BT77 mount. You would screw them directly into the speaker cabinet. As an option, there are holes in the bottom mount that you can use, so you would only have holes in the bottom of the speaker rather than on the sides.
Just some thoughts.
-Lou