Final update: I've spray painted a logo on to one side so that I can easily identify when it's upside down:
And, it was weighing in at 151g. Maybe that's close enough to be arguable, but I'd rather be strictly under the limit, and I certainly don't want to be forced to start hacking bits off it at the start of the event.
The nuts I've used are 5mm tall PCB standoffs, and they add a combined mass of 3g to the robot (as pictured). I spent 15 minutes carefully grinding these down on the bench grinder and managed to reduce them to a combined 1.5g (not pictured), so the robot is now nicely underweight and I'm completely ready for AntFreeze
