I use 14.4% preboiled with some citric acid. EG if I use 600 gr sugar I bring it to a light boil ( just above simmer) for 25 mins with 600 mls of water and a pinch of citric acid. I then add it too the boil at 20 mins before flameout. I dont want the sugar solution to turn colour while inverting it with citric acid for the CPA.
BTW a CPA is not a CPA if you dont use a yeast cultured from a CPA bottle.
I have experimented with small amounts of sugar additions in other brews but it generally is not true to style.
I have to agree that a small sugar addition makes for a swiller if you use most of the ale yeasts.
When all things are taken into account, I guess we all know why the Germans didn't allow sugar in their beers.