All you need is a flexible mind, I've mixed and matched units most of my working life, working with people from all over the world at the same time, even now at home we think in different units. I think in metric but explain to my wife (ex US) in ft/inches and with the neighbour who hails from the UK in Imp. units. Real measurement wonders are the number of "tonnes" used by the shipping world (5 or 6 that I can think off) and the Swedish mile (still seen occasionally on rural roadsigns) that will get you at 10k when you think you only have a mile to walk. A neat transfer campaign was run in OZ in the 70's on the Redhead matchboxes, Think Metric with samples :).