I have a truckmount and a portable,Here have a look and see a TM operator with lots of overlapping
And it does not matter which system I use I will always overlap/multi pass.
I do NOT understand how some guys are able to just do a single pass and think they are actually cleaning. I get paid very good money to actually Clean the carpet so I do what ever passes/overlaps I need to leave that carpet clean. One pass is just not enough, especially on a nasty super soiled carpet.