I recently tried to make one and it missed the mark. But here are some things I learned. There was some good (and not so good) info in this thread
. The numbers that were taken from BLAM should be correct so you have a lot of info right there.
Chimay is a bit different than Westvleteren or Sint Bernardus in that Chimay doesn't use dark syrup, just dextrose. So you have to get almost all your color from malt. Chimay uses 'something' to adjust the color to account for differences in the Special B, that's allegedly the 'malt extract' mentioned on the label. Sinamar fits the bill here, but it should only be a tiny amount.
I used this recipe:
11 lb (73.6%) Belgian Pils
.75 lb (5.0%) Belgian Crystal 45L
.75 lb (5.0%) Belgian Special B (~115L)
1.5 lb (10%) White Wheat malt (German)
.75 lb (5.0%) cane sugar
.1875 lb (1.3%) dark caramelized syrup (homemade)
Styrian Goldings to hit ~30 IBU
~400mL washed slurry of WLP500
This beer wasn't dark enough and didn't have enough of the dark caramel/fruit flavors. If I were to make it again I'd probably eliminate the C45 and increase the Special B (and not use the syrup, I only added it because I wanted to use it up and wanted to make the wort more fermentable in the fermenter) and use a tiny bit of Sinamar or Carafa Special if I didn't have Sinamar. Maybe increase the hops a bit, hard to tell since my FG wasn't quite low enough. The SRM can sort of fool you on these beers, they are actually darker (i.e. they have a higher calculated SRM) than you would expect. I think it's because there is so much red and not as much black in the color. I'd also mash for higher fermentability. I think that's necessary to reach 88%-89% apparent attenuation with only 5% sugar and Chimay yeast.
IME, Chimay yeast isn't the most forgiving Belgian yeast there is. I get a slight solventy note even though I fermented it relatively cool (mid 60s). HTH and good luck!