Welcome to ModelEngineMaker !If you have problems registering or logging in, please use the contact menu option to request assistance.
I'm never happy with going undersize on both. If you go for 75% when drilling and tapping and then also do the same with the male part that's 75% of 75% which is only 56% engagement so usually make the male full size though suppose it depends on the application and what loads you are expecting the thread to take.