The purpose of tie down compensation is to make safety slide to within code limits. Not sure it was a code requirement or not. Otis used tie downs on 800 FPM and above. A 750 FPM car did not have tie downs. I was an Adjuster at Otis back in the 70's. I remember the Regional Field Engineer telling us about Armor having trouble with Safety slide. He said they did not have tie downs. You might want to get some reports from your State or City on Full Load tests for the units in question. Also check crosshead data tag & test forms to be sure speeds were not reduced.