I followed these instructions ages ago, but it didn't seem to take. Found other ways around the issue of typing with macrons - until one day I noticed the "MRI" in the taskbar where it normally said "ENG". Somewhere along the way it had all worked out.

In my Legacy database I type them as 'normal' and use the program's settings to capitalise when I want that. When I'm writing to a person, I'll capitalise at least the first time I use a surname.