Scale pitch CV from Microbrute (0-10V) to SynthKit (0-5V)

Awaiting the new CV bit, I used the hardware development kit and a potentiometer to connect the Microbrute pitch CV to play music through the littlebits. After tuning the potentiometer, I get 3 octaves almost unison between Microbrute and SynthKit, but beyond that the pitches are not fully matching. Is this just a matter of an imprecision in tuning/potentiometer, or do we need a different approach? How would the CV bit work?