The last time I spoke to Standley Goodwin about building a M to International standards and racing here in the USA, he said no problem. The only differences are the International is in metric, the US is in imperial (the measurements are the same either way). But there is keel depth restriction on the International. That's it.
Personally, I think we should just use the International rules and be done with it. Metric rulers are really inexpensive BTW. Most of the time you just have to look at the other edge of Imperial rulers.
This is one of four R/C sailboat classes that have international standings with the ISAF (Marblehead, One Meter, 10 Rater, A-class) so we really shouldn't "rock the boat" per say.