Dragging this back up to see how they turned out. Brewing the westmalle clone tonight, 12 pounds pils with 3 pounds sugar, trappist high gravity slurry from a Belgian pale I made last week.
It came pretty well. Below is a side by side with Chimay triple.
The Chimay is darker and has less yeast character than I remembered (it's been a while since I've had one).
Compared to mine, Chimay has a rounder flavor and a thicker mouth feel. I think it also has more of a bready flavor whereas mine tends towards light fruits. The alcohol sweetness was very similar (Chimay is 8% ABV and mine is 8.5%).
I like the Chimay better, but I'm happy (and a bit surprised) with how well mine holds up. Maybe I'll pick up some Westmalle for further comparison.