I have the multiwheel topas IATA, travelling on BA at least once a month have no issues using it as a carryon along with a laptop bag.

I have also recently used it as a carryon with RyanAir flying from TFS to BHX with no questions at all. In addition in the 4 mths I have owned it I have carried it on to Air Berlin (Y), Etihad (J), Monarch (Y) and Japan Airline (Y) flights.

The only time I checked it was last week on an AirPhil Express flight between MNL and MPH on a Bombardier Dash 8 Q300 as I was also carrying a NorthFace Surge Backpack, however on other flights I have had no problem carrying both the backpack and my Topas on BA both ET & CW and JAL Y.