Hello,
for the XLS+ we use Supplement 16 (Operational Dispatch Planning Performance) for planning which contains 1.67 and you can do 1.15 in addition for wet.
That is approx. 500 ft shorter than AFM Chapter 4 multiplied by 1.67.
Thats the shortest legal way for commercial operators we figured out
XLS the Supplement 30 (CFR and JAR Operation Landing Field Lengths) was basically doing the same thing.
Good flights
Oelknarre