I rented a car from Avis in Australia in March 2007 using N744100, which I had gotten from British Airways & lowered my "excess" ( =deductible) from the normal A$2500++ to A$1000++. I scraped the fenders against wooden stumps too short to see , so upon return they charged me A$1240 incl. GST, airport concession fee, & 1 other tax.
Back in the USA I filed a claim with DC, which denied it on grounds that I had "accepted" the automatically included LDW !