It is different how sweet you prefer a dish like this. My dad would always double the amount of sugar compared to me, and my brother would add a lot of sweet biscuits to it. I love the gentle sweetness from the rhubarb syrup, which will also vary in sweetness depending on your rhubarbs and how thick and intense you make the syrup. My point is that you need to carefully adjust the sweetness of this according to your preference – more or less syrup – it is up to you.