I think ChocolateBike wins the lighting race.
A wingnut wouldn't help - I'll only ever be transferring it at home and with this setup I just need one allen key.
After the ride home, I've decided it needs something to stabilise it - I'll probably make up something with epoxy putty.
One benefit of this rig is that all the lights are forward of the cables, so I don't get any glare from lights reflecting off cables. It's surprising how unpleasant that can be when you wear spectacles.
Oh, and Panoramix, the tribars were manufactured with a 5mm hole there.