Ive got "The Most Thorough...." right across the top and back of my van. Ive had it on there since doing the Fast Track, around 12 years ago.
Ive only ever had two, strangely enough within two weeks of each other, try it on. I knew I had done a great job for them and after more than 20 years in this business at the time, could tell were con merchants. I addressed their issues with the clean, got paid, left and never heard anymore about it.
2 out of around 7,500 jobs done is hardly worth bothering about, even if they had not paid up.
Dave.