Thanks for the replies!!
I am really impressed by the numerous and very qualified replies to my question.
OzExpat:
Where can I get more information about the voiding of the companiy´s insurance policy? That is really interesting!
FlyinWithoutWings:
As a matter of fact I relly fly a 737/300. I know about the recommendation in the Boeing flight manual to set the MDA in the MCP window. I also think that is the better - and safer - way to go.
I will try once again and make the proposal to change the procedures to what seems to be international standards.