It's not easy to tell from the picture, but I re-built the weapon (again!) using a chain-sprocket drilled and tapped to accommodate two hex-bolts (one of which also functions as a beefier set-screw for the shaft). The newer weapon has better balance (and thus less vibration) than my earlier attempt. I perma-installed roller bearings to hold the shaft and, finally, added a piece of thin plastic on the backside to keep the guts from falling out.
I hate how the kill-switch is hanging out. It will be an Achilles Heel if I go against a saw weapon. But I can't come up with a better way to mount it and still have it accessible.