There's a couple of points here :-
1) Howard is giving a presentation on Saturday about the SDX. It's almost inevitable that somebody will ask about an analogue backup, and it's right to ask the question. Howard simply wants to be able to give the official answer.
2) SDX will fly on P3E which is an excellent proving ground for this technology. It will also fly on ESEO, which is due for launch in 2008. ESEO will go into GTO, so it will be another good proving ground, although how much service it gets before Eagle is ready is unknown.
Seems to me like there are two options :-
A) Plan for 2 SDXs + ACP, with no analogue backup. Risky, but by the time Eagle is ready P3E and ESEO will have been in service for some time. This will either give everyone confidence in the technology or give us an opportunity for a re-design if it fails. And of course we test it properly in advance.
B) Plan to fly at least one analogue backup.
Either way, don't miss Howard's presentation - if you haven't seen the SDX working, you'll be in for a real treat!
regards
Grant