[slob]

Just remove the white/red wire completely for no charging light, or as you say connect it to the + side of the voltmeter should work, although the charge light is much simpler. I don’t think Pin 2 will ever reach a higher voltage to show you overcharging, I’d be more inclined to do away with the white/red wire and connect the + side of the voltmeter to the battery side of the main fuse. However I’ll ponder that for a bit, there may be a better way. Are yiu going to keep the bike on an optimate? a voltmeter might want isolating with the ignition switch so it doesn’t slowly drain the battery.
I’m guessing you’re doing away with the sidestand warning too, so you can lose the grey wire too.
Then the blue/black to the clocks only needs to connect to the oil light, which still has white/yellow running back to the oil pressure switch.

Obviously I’ve stuck to the colours on the diagrams, you’ll have to translate to what’s in your loom yourself.