Thanks - good to know.
The way I'd read the recipe was to add an extra pound of sugar to the base dubbel (so 2lb/5G) and ferment on 5-10lb/5G each of both sour and sweet cherries.
Here are my notes from the 1st attempt. You'll just have to compare these to the recipe you have there. I brew a lot and can't really answer many questions - just can't remember it all. It's why I keep notes like this
[19MAR17] OG 1.058. Only 1# piloncillo added. No brown sugar added. Ground cinnamon was used instead of stick. 14.5# Cherries will add exactly 10 gravity points.
[later ?] I did add brown sugar
[19MAR17] taste wasn't as sweet as expected. Good flavor though. Cinnamon was not too pronounced, which is good.
[18APR17] 1.008. Taste was not sweet, fairly cherryish. Not super tastey I don't think. Probably needs more ABV.