[fovea1959]

...and giving up. Doesn't matter what I do to the code in ARDUINO\library\Wire\, nothing seems to change. I even put deliberate syntax errors in there so that the compile would blow up (to verify that my changes are being compiled), nothing happens, so it appears to me that simply fixing ARDUINO\library\Wire\utility\twi.c doesn't make the changed source get recompiled and linked into the final program.

Not familiar enough with the Arduino build process to understand how to make the patch happen. Everything I Google indicates it should just be change the library source code and reload....

Will use your workaround...