I am appalled by the views that indicate deviation from manufacturer’s advice is to be expected. This is a facet of a hazardous ‘I know better attitude’. Accepting that because something appears to work it will be satisfactory and thus the risks associated with it remain unchanged, is very false safety.
When you encounter one of the remote situations which the manufacturer has had to consider, and possibly demonstrate, deviants will be exposed to the same unknowns of a test flight.
Even a simple mis-judged trim-up might increase the risk of floating, which in the wrong circumstances could result in an accident. Alternatively a tail strike – what defense would you offer your operator against being charged the cost of a repair. A trim-up may skip the weight on wheel / spoiler / reverse / antiskid logic; this won’t be classified an engineering system failure – it’s a ‘wetware’ failure, and the tag of wet behind the ears (inexperienced) would suit the pilot, because in that situation s/he was inexperienced.
Above all else, pilots should look for a safe landing - not a soft one.
Autoland systems trim-up for good reason; the risks in this have to be quantified and judged, and procedures developed for operation.
Similarly crew operating procedures for manual flight are not limited to engineering decisions; they involve all members of the flight test and certification team, the regulator, particularly training Captains and those member pilots of Operations Assessment Boards.
If an operator believes that a change is warranted then there is a process for this; it enables review and experienced cross checks, pilot and engineer.
It does not encourage or condone an individual’s self-appointed risk assessment.