Enable RDB mode and Surfaces/Sectors/Reserved
 

I noticed a small problem with the hardfile settings window. When you click Enable RDB mode, the button is greyed out and the values for Surfaces, Sectors and Reserved show as 0.

If you then manually edit one of those three numbers, RDB mode is disabled but the Enable RDB mode button is not un-greyed out, so you can't re-enable RDB mode. You have to click OK or Cancel and reopen the hardfile settings window to get the Enable RDB mode button to be clickable.

It might make sense to change Enable RDB mode from a button to a checkbox, and have the Surfaces, Sectors and Reserved number fields disabled/greyed out when the box is checked.

RDB mode is equal to Surfaces/Sectors/Reserved = 0, so you don't need the button.

However, I would prefer to grey out Surfaces/Sectors/Reserved in RDB mode and change the button to "disable RDB mode". The disable button when clicked should set Surfaces/Sectors/Reserved to what they would be set by "add hardfile".