my cables arent long enough to mount the can-bus on the lower part of the leg where it is vertical. does it need to be mounted vertically or are its internals orientation sensitive?

The canbus cable and editor doesn't need to be vertical. It doesn't care about position or orientation at all (think of it like a USB cable).  

The compass on the other leg does need to be oriented correctly or else your flight will be erratic and difficult to control (at best), however.