There’s pro’s & con’s to the exhaust on either side.
Inlet on the motor is to the right so carby and airbox are more to the right.
Right hand side the pipe has to sit low to fit under the airbox and then turn upwards as early as possible to clear the tyre at full compression.
Left hand style (which Aberg used) pipe is able to sit higher at the rear as it doesn’t need to fit under the airbox so it exits around the shock higher giving more wheel clearance.
Left hand system has smaller muffler but has tailpipe behind the muffler which helps sound levels.
Right hand system has more room for conventional type muffler.
What ever floats your boat.
78 NVT (UK) models had left hand system
79 NVT (UK) models had right hand system
Early Profabs seemed to have left hand systems
Later Profabs seemed to have righthand systems