Yep - saw it first hand during a few steepies at 60* AOB during a test flight
we did after a D check (we were gettin mighty bored!)
Just use your VSI to keep the nose where it should be - soon as it so much
as twitches make an immediate but small correction. Keeping a bit of
bug-poo on the windscreen relative to the outside horizon helps after
established in the turn, but the VSI is your first giveaway. Don't rely on the
FD-108 because it lags a bit when over 30* AOB. If I recall correctly it
should be turned off anyway. Displayed A/H attitude I think varied by about
a 1/2 degree when over 40* AOB level.
Lotsa fun if you get the chance!
eckhard a gyro will translate 90* to a real or apparent disturbance through
precession as you have mentioned. Same on 737 - no bank angle error just
pitch, but a constant error in this case through a 360 (as long as IAS remains
constant).