Someone like JohnS may hve a different view but my understanding is that a drilled hole will always be slightly bigger than the drill size. to get an interference fit you need to drill the hole smaller, but it will depend on the dowel tolerance. Looking up a typical dowel its +0/-.005mm. If I read the tables right you need a .01mm smaller drill e.g. 1.59mm for an interference fit in steel, so maybe smaller in acrylic - 1.58mm maybe?