My experiment wasn't very precise, so I'll defer to your numbers, and you've covered your bases by rounding to the nearest bar measure. I'm a math and sometimes physics guy, not a chemistry guy, so we're at the limit of my knowledge. It looks good to me. There's variability in the numbers anyway depending on the fineness of the sugar, and at the end of the day we're adjusting to taste. Thanks for the conversation!

This little experiment also helps justify why rich syrup is superior: It takes about that much water to break down the sugar, but doubling the water content to make 1:1 syrup just adds to the volume, it does almost nothing to dissolve the sugar further, it's just watering it down.

Ok I mixed up some of each and measured the resulting volume, the missing factor is how efficiently the sugar dissolves. 120ml of water and 120ml of sugar yields about 180ml of 1:1 syrup, and 60ml of water and 120ml of sugar yields about 120ml of 2:1 syrup, so the ratio is in fact 3:2.

Your chart is correct, the only real adjustment is that 2:1 syrup is 1.5 times as sweet as 1:1 syrup.

This would also be consistent with your 1.33 times as sweet statement, as 1/2 x 1.33 = 2/3.