uneven floor

I cleaned a restaurant last weekend that did the same thing....spotty and uneven floors. And we all know that cleaning commercial grade caarpet is hard as hell to do. I told the owner that b4 I even started we were going to have a problem with streaking/spotting bcause the floor is not level. I also made him acknowlege what I was telling him by having him sign the estimate sheet. Anywho........when all was said and done the floor didn't look much better than before. He of course said he didn't know it was going to streak/spot and then I showed him the estimate he signed.....suddenly his memory came back. I use a rotovac on almost all my carpet jobs but it's not very good on commercial grade carpet. I thought about the RX20 myself. You can hook it up to a portable unit. I use a portable Ninja 500. GREAT MACHINE and more suction power than a lot of van units. However....I myself am looking for a good machine to do commercial carpet with. Anyonw have any suggestions???

  I clean carpets with a ambassador pull type carpet cleaner.  This machine has a 17 in width.   I have cleaned a high traffic restaurant twice in 6 months with no complaints from the manager, although I knew that the carpet looked spotty, but couldn't figure why as this hadn't happened to us before.  I finally realized that the floor is uneven & has dips in it. This is causing us to lose all the suction over these spots. Obviously we can not use this machine for this job any more. I do have access to a older rx-20. Can I use this with a portable machine.  Would this be the way to go without  haveing to spend a pile of money  on new equipment. The girls that clean carpets with this machine really like it & say they don't want to go to a wand type machine.