Trent 972
My apology on KIAS
I assumed it was corrected data for KIAS, TAS seems more likely now you mention it. Would've been handy if the report had made it a little clearer.
Up into the Air
Be careful on the 5 to the live notion as it is somewhat of an OWT.
Detail can be found in the FAR23 certification standards, which is where it was born from. 5 degrees is a certification requirement.
Reality is for low performance twins it is typically less.
John C Eckalber's book "Flying High Performance Singles and Twins" gives detailed explanation on this as well as methods for calculating the optimum angle for each type.
Apparently research has shown that for every degree off optimum the loss is about 30 fpm and the typical light twins zero side slip angle is around 2 degrees.
How we as pilots will ever be able to fly that acurately in a real assymetric scenario baffles me, but there it is. Perhaps as I mentioned earlier we just need more quality time with one feathered.