My question is why would you need a diacetyl rest for a Belgian strain? In my experience diacetyl is common in lager and English yeasts, but I have never encountered it in Belgian yeasts. Acetaldehyde, yes, if removed from the yeast to soon before it finishes fermentation and cleans up by-products. Also, pitching at that high of a temp would more likely produce acetaldehyde vs. diacetyl.
FWIW, I rarely do a D-rest. Even on lagers. I you pitch an appropriate amount of yeast and ferment on the cold end of the ferment temp, the yeast will eventually clean up the diacetyl and other by-products of fermentation.