Safari 4: Setting F5 to reload page. Possible?

Being so used to hitting F5 to reload/refresh a page in browsers (I still use FF under XP at work) I tried using keyboard shortcuts in Prefs to change it in Safari.

Restarted Safari and the View menu showed F5 next to Reload Page instead of Cmd-R - but it didn't work (I also tried Fn-F5 and that didn't either).

Is this possible? If there are reasons for not using the F-keys in this way surely it shouldn't allow you to set them up?

BTW, I'd prefer to have F5 in addition to Cmd-R, is this possible?

 

Thanks - at least I know I haven't done something wrong.

I know, that's why I want it in Safari as well