Horchata ratios that hold up when you make it in volume

Made this for a party of forty last month and learned that the home recipe does not scale linearly. At home you soak rice and almonds overnight, blend, strain, sweeten to taste. At volume, sweetening to taste is where it goes wrong, because you taste it warm at the start and serve it cold four hours later, and cold blunts sweetness by a noticeable amount. I underdid the sugar by about a third and had to fix it in the jug in front of people. So: sweeten it, chill a sample, taste the sample, then adjust. Not the other way round. Also strain twice. Once is fine at home and gritty at scale.