Ok fair enough, it's been 30 years since ATPL in Oz but now you jog my memory 1.67 does sound familiar.
Our mob use a safety factor of 15% on top of the distance for in flight calculations from the Airbus approved QRH tables simply because we are not test Pilots operating in a test environment day to day after flying all night with no sleep.
I used the Airbus Fly smart App which also adds 15%
I can also use the ACARS landing data request function as well which also includes 15%
In an emergency we can ignore the 15% if the commander wishes.
From our FCOM Perf section:--
IN-FLIGHT LANDING DISTANCE The flight crew should use the Landing Distances published in the QRH as the reference for In-Flight landing performance computation. The In-Flight Landing Distances reflect the performance achievable in a typical operational landing without margin, assuming realistic airborne phase from threshold to touchdown and deceleration on ground to full stop. The In-Flight Landing Distances consider: ‐ Touchdown within the touchdown zone ‐ Maximum manual braking initiated immediately after main gear touchdown ‐ Normal system delays in braking activation in case of autobrake ‐ Prompt selection of max reverse thrust, maintained to 70kt, and idle thrust to full stop (when credit is used) ‐ Antiskid and all spoilers operative.