I sweeten my grapefruit wine with a homemade cordial made from sugar and fruit/zest...
citrus wine made using zest still has a bit of a bitter undertone without sweetening.
If I use too much juice and zest from citrus fruit, I have a damned difficult time getting it to ferment.
especially lemons. ( horrendous to get fermenting)
Grapefruit ferments easier and makes a better drinking wine.
I use 4 litres of water in my citrus recipes ( per gallon) If I used pure grapefruit juice for the must, it simply would be too high in acidity to ferment.
( in my opinion, using NZ fruit)
Allie