It's definitely good practice to oversize holes in water, laser and particularly plasma-cutting. For K-Cut (water), I find 0.5mm over about right on average (for minimal cleanup) or around 0.8mm over if you want 0 hassle. Of course, this lowers the overall accuracy of your assembly so shooting lower and expanding the holes exactly might be desirable. Dremel tool with a carbide burr works nicely!