Hi Martin,
According to our developers, then making the same modification to the RadioButton control will require approximately the same amount of work as it did require for the Button. A permission to reschedule it to version 6.4.0 Release d is being sought, based on that information, but I do not have any definite response on that yet.
Please track the entry and watch for rescheduling, should it occur.
Sorry, but this is the best I can do for now.
Palli