Ya I was hoping to add less volume that way.
For backsweetening wine, I don't use syrup, just plain 'ole cane sugar -- I use a drilled mounted stirring rod and pour a very thin stream into the wine, and have no problems with it dissolving. However -- like Fred I don't backsweeten many wines, and my version of "sweet" is pretty dry to most folks. Depending on how much you're sweetening the wine, this may not work as well, although it adds the least possible volume.
I work in 1/8 or 1/4 cup increments, stir the sugar well into the wine, and taste. Repeat as needed. There is an element of risk in backsweetening the entire batch like this, but there is also a risk is messing up the calculation when bench testing with small amounts.
When making liqueurs like limoncello, I make syrup, but I'm also intentionally adding volume to reduce the ABV from 40% to 30%.
Also, when making simple syrup, don't add sugar to boiling water and don't boil your mixture. Mix the water and sugar and simmer until clear. Otherwise you are making rock candy. As noted, the max really is 2:1.
I've never saved 2:1 syrup when I made it, I always added it all in, so I never realized it would make rock candy. Interesting!
For my last batches of liqueur (cherry cognac and leftover limoncello base) I made a 1:1 syrup, as I prefer less sweet. I goofed and had a cup of syrup left over, which I put in a bottle in the fridge. I used it up in other things over the following 2 weeks. I 'spose if it had been a 2:1 syrup, it probably would have crystalized.