Was considering buying this unit for a 10 gallon I had running. Found a few threads stating similar complaints about lack of skimming in comparison to the nice results of the big brother and pro versions. So I called them directly and asked, the guy at AquaC was very nice. This is what he told me.
In their testing, their seems to be a correlation in skimming efficiency with pump size and internal dimensions. They noted the Remora Pro with Mag3 was optimal. I always assumed the bigger the pump, the better the bubbles, the better the skim, they stated that this was not true, the dimensions of the internal design seems to work better with a certain rate of water. They went on to state the nano skimmer was not as efficient for the reasons mentioned above -- internal dimensions to pump size -- but stated it was a good option if you needed a skimmer that would not overheat or over power a small nano tank, like a pico. The Remora Regular with maxi was also rated high. He also stated the extra large collection cup option is not a good buy, as the tube dimensions were not optimal in thier testing for best skimming, he said stick with the cup that comes with the unit.
So I ended up buying the regular with maxi, it works really well. Took a week to kick in and for sound to be reduced. I added the paper towel mod and it can not be heard at all -- literally, the water trickling is louder.
I must say, I really like AquaC, they came off as honest and true to the hobby spirit.