In Eden Studio’s WitchCraft, they use the IS, but give a conversion note in the Convention section at the beginning of the book:
“Measurements
This book primarily uses U.S. measurements (feet,
yards, miles, pounds, etc.). Metric system equivalents
appear in parentheses. In the interests of ease of use,
the conversions are rounded relatively arbitrarily. For
example, miles are multiplied by 1.5 to get kilometers
(instead of 1.609), meters are equal to yards (instead
of 1.094 yards), pounds are halved to get kilograms
(instead of multiplied by 0.4536), and so on. If a
Chronicler feels that more precision is necessary, she
should take the U.S. measurements provided and
apply more exact formulas.â€
I feel that it works well.
I also like that they switch gender each chapter:
“Gender
Every roleplaying game struggles with the decision
about third person pronouns and possessives. While
the male reference (he, him, his) is customarily used
for both male and female, there is no question that it
is not entirely inclusive. On the other hand, the “he or
she†structure is clumsy and unattractive. In an effort
to “split the difference,†this book and all books in the
WitchCraft line use male designations for even chapters,
and female designations for odd chapters.â€
