I started the car today - what a difference!
Beforehand, I had set the float level at around 16.5mm on the 7g floats and was getting an inconsistent and unreliable fuel level, but maybe around 30mm as far as I could tell. The engine was barely running, and sounded like a sack of hammers - it would reluctantly start, more or less idle without choke, but had to be very gently coaxed up the revs or it would cut out immediately, and was spitting back badly. It would cut out completely after about 5 minutes. I had balanced the carbs as best I could and improved it slightly, but it was terrible, no chance it could be driven.
It's sooooo much better with the 8.5g floats and the 27mm fuel level. It starts very enthusiastically, and revs up no problem. I haven't tuned it yet, but had the vacuum gauges attached anyway so roughly equalised the two carbs.
The car isn't on the road so can't be properly tested. I also suspect compression problems, and haven't even set the ignition timing yet. But the fuel level was definitely at the root of the poor running. It sounds like a runner now - a bit rough, but a runner! 🙂