So all in all I don't think we should use it unless we are doing a CAT II or better.
Do you mean CAT II or worse (i.e. CAT III etc)? What about where it is a CAT I approach with a Rad Alt DH?
I like the method used by Capn Bloggs, and IMO it is the only one that can work reliably on the line.
The only one that can work reliably? So setting a negative value (as many, many operators do) doesn't work reliably?
PP