Whilst shopping for tea, some other thoughts occured, which I missed in my previous post and are relevant to this discussion...
Take the (extremely simplistic & fictional) case of a pilot with, lets say 10,000 hours muti time in (only) a C337. On the face of it, an extremely well-experienced and competent twin pilot.
However, put that same pilot in a more 'conventional' twin, lets say a Seneca which suffers an engine failure at or shortly after rotate... that pilot is going to have precisely NO IDEA of how to handle
assymetric (that term again) thrust. The consequences would (probably) be tragic. That is (in part) reason enough to log centreline-thrust aircraft as single, and predominantly the reason I stand by my original post.
I'm sorry -I fail to see your point with regard the B-777? and, I quote:
for a non centerline thrust multi engine instrument rating demonstration
I was never aware of such a "non-centreline-thrust multi-engine IFR rating"... when I did mine it was simply multi-engine IFR, with the condition that a centreline-thrust aircraft was not appropriate for the flight-test -again, because of its lack of assymetric thrust 'attributes'. Has
that much changed in Aotearoa of late??? The rules and reasons always made perfect sense to me.
My recommendation (for what it is worth) would be to make certain with your local regulator that logging multi time for centreline aircraft is indeed appropriate.