I've carried camping gear that weighed as much as a second rider before and didn't really have any issues. Handling is different of course and hills are a little more laborious for the motor, but it's all good.
I think maybe 250 miles round trip for me... But people have taken these things on 4,000 miles journeys at a time. Just make sure she is in good mechanical condition and let her rip. If you're concerned at all, just slow down 5mph. (Though, with the mighty GZ, you may not have a choice than to slow down
