So I've been drilling and trimming, and doing some filing too.
Setting up for the main pivot hole, I decided to shorten the distance between the front adjuster plate and my earlier mark for that hole. In so doing, I moved the drill mark forward, and trimmed an additional quarter inch off the back of the pivot arc. This also had the effect of moving the rear set screw tab further back, such that it will now hover squarely above the kickstand tube. The bracket's also gotten lighter, which is nice.
Sketching ideas for how I might also reduce the width of the front adjuster plates, I settled on just cutting a straight 1/8 inch from their left sides. In hindsight, I wish I'd gone with the double-lobe design, as it would have allowed more room for the hook hole still needed for the kickstand's tension spring. Considering the clearance necessary for that spring's smooth operation, it remains to be seen whether a hook hole in the front plate is even an option anymore.
Anyhow, I'll next be drilling the rear set screw hole, and maybe even that spring hook hole. I'll also be tapping all necessary threads. But here are some pics of the progress described.