i have a golden strong and a dark strong brewed on the same day that are in 2ndary right now. they're 8.1% and 9% respectively and both attenuated to about 78%, which is much better than my first belgian. the thing i changed is adding the sugar at high krausen. of that 1.089 OG estimate you have, i'd guess about 30 points is from the sugar. if you pitch into a 1.050ish wort and let the yeast get going nuts and chew up some of that sugar and then add the sugar the yeast will be much healthier and they'll get you down really low. with that much sugar to add, i'd recommend adding a pound every 12 hours or so once high krausen has started. i didn't bother boiling it or anything. if its that hard style belgian candi then i'd give it a zap in a clean blender. it powdered up pretty fast for me. the flip side to doing this is that a 1.089 wort to start with isn't that big for the yeast, especially if you pitch from a big starter. the other thing is that the stress the yeast will go through in a wort of that gravity creates some of the estery flavors you expect in a belgian, but also the fusels. the_bird's suggestion of starting fermentation low is spot on for preventing stuff for that. i suppose all you can really do is decide on a course of action and take a lot of notes on things like pitch temp and ferm temp and pitch rate, and see how it turns out. let us know how it turns out!