Mark, do you clean much deep sculpted berber? Not just berber, but the real deep sculpted stuff. I have to deal with a lot of it, and if it has been badly neglected it is usually a nightmare. Pads skim over the top of the crevices. A carpet wand doesn't get maximum suction. The scrubber that I have doesn't have long enough bristles to dig the crud out. What do you suggest?
If you have any of the Fiber-plus pads from Excellent-Supply, you might try these. If you dare, you might even also try their Fiber-max scrubbing pads, but these are VERY aggressive. I suggest discussing matters first with the customers. Are their expectations realistic? Are they prepared to throw in the towel and tear this stuff out if it proves to be not-cleanable? Or if your scrubbing causes some difference in carpet appearance? You need to know when to hold them, and when to fold them in any business or endeavor.