OS Max-S 35 Venturi

As I'm having a venturi made for my Flash 35 (OS Max-S clone) I though it'd be better to move the OS Max-S venturi to the Flash and put the new one into the OS - what dia hole should I specify?

Best to start small and open it out?

If you are using a current OS needle valve assembly (.135) try about a .260. If you are using the old OS needle valve assembly or an ST type (.155) try about a .280.