a bit more information would help us help YOU 
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Is it correct to assume that you are successfully acquiring you sensor data connected to your Arduino Mega?
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Your issue lies with transfering data between the Mega and Maxi controllers. is this correct?
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the
Wire libraryis for I2C communication. Are you trying to transfer data between the controllers over I2C?
If that is the case, I2C works best when units are close to each other. For longer distances, Serial communication (or RS485 of even longer distances) would probably be better suited to transfer data between the controllers.
You may want to have a look at this good tutorial on using Serial communication for transfering data between controllers:
Serial Input Basics
hope that helps...