Discovered (i.e.: read the last bit of the recipe properly) that the correct temp for fermentation is more like 25°C rather than the 18-19°C i originally thought - and needed to maintain to contain the overflowing krausen
So ~2/3rds of the way through the fermentation i started ramping the temp a degree per day up to ~24°C yesterday.
Also did the syrup additions in 2 lots. The first was ~2/3rds through the expected fermentation, SG ~1.030. The 2nd was today, when the SG~1.018.
I increased the syrup addition from 1.14kg total to 1.5kg total (so 2x 750g additions), to compensate for what seems to be a slightly low OG (1.069 down from the expected 1.076) - should add an extra 4 points.
Ideally i would've added the 2 additions a little earlier, say ~40% remaining attenuation rather than 30% for the first one; and the 2nd addition a day earlier to be more like 30% remaining attenuation. These additions were delayed as i wasn't sure if the first one would cause another krause explosion. In hindsight, this wouldn't have been a problem.
Also, when i repeat this i'd start the fermentation ~4°C higher and maintain that, as it's expected to improve the flavour/aroma profile. I guess i'll wait and see as to whether my lower fermentation temps has any significant impact.
Finally, on further research, i also realised that the D2 we're using is a bit lighter in colour compared to the CSI D-180 that the recipe is designed for. I'm inclined to think (/hope!) that this won't have a large detrimental effect on the flavour/aroma, largely because the D2 is from one of the main candy syrup suppliers in Belgium so it's of the highest quality & i'm assuming it'll have all the depth and complexity that we want. The only real difference is our clone might be a little lighter in colour. Also, assuming Westvleteren use D2 or something like it, i can only guess they use a little Spec B or more D2 to achieve the colour of the original Westy 12. Another option to compensate might be to use a little extra D2 for priming - it's effectivelyan extra 100-200g into the recipe.
Hydro sample smelling and tasting fantastic!