What tool are you using to sync your carbs? Due to room restrictions I dont think I will get the snail type one in there so a remote one would be the go. No, my ears are not good enough to do it without a tool...
As Danny said, just remove the plug over the progression holes and shine a torch down the throat or whatever it takes to show the butterfly through the holes. Adjust until they are aligned. Simples.
I use a 40mm pvc 90 deg bend with one end cut down and rapped with electrical tape (fits into ram tube) The other end stands vertical and slips over the flowmeter. Works for me.