There was considerable discussion on the John Welsford builders forum about the metric system and metric tapes. Two prevailing opinions came out of the exchange: 1) The metric system is much easier to use, once you learn it, and 2) When building a boat, you want your tape measure to have the same system on both sides of the blade.

Unfortunately, it is almost impossible to find metric-only tapes here in the US. None of the retailers I tried had them, and it is difficult to find them on the internet. We finally found a manufacturer who makes them (Starrett) and bought enough to sell.

As kind of a weird sidenote, all the metric-only tapes we found had English blade widths, as these do.