I don't know about rum. The OG of my juice was like 1.035 so I jacked it up to 1.056 with the sugar (disolved in as little water as I could; it was like runny syrup when I added it to the juice) then pastuerized at 1.022 to stop fermentation and maintain residual sweetness. I don't think any taste is due to what type of sugar is fermented because that is converted to alcohol and CO2. Any taste would be the result of the unfermented sugar which, in this case, tastes like sugar. I'm thinking about trying a similar set up with brown sugar to see how the molassses fares tastewise. I'm hoping that KISS v2.0 recipe is posted soon. He says it'll be a close clone of Angry Orchard Crisp.