Due to the sugar in the pineapple, the brix at 2:1 as described is high and I find dialling back the amount used in drinks necessary. It also precipitates sugar (for the same reason) and requires gentle reheating periodically. It would be worthwhile using a refractometer to remake this at a target brix.
Great recipe for the roasted pineapple syrup. I found the juice yield increased when I just pressed the pineapple chunks through a fine sieve by hand (and then poured through a chinois). I used the left over pulp to make roasted pineapple leather for a garnish for another drink where I also now use the syrup. I also make it as a 2:1 (by weight) syrup with 50% raw cane sugar and 50% white (or the pineapple is smothered).