Problem is, the manufacturer has no control over what ends up getting towed. An unscrupulous owner could claim they were only towing a small rowboat on a trailer when in fact they were towing something much heavier that damaged the frame. Northwood is famous for building their own frames from heavy "I" beam steel and I would imagine a properly designed and installed hitch used for towing a light load would not add any undue stress on the frame. I believe their warranty is 1 year so I would guess you could add the hitch then since warranty issues are moot. It's also illegal to tow doubles in Oregon so Northwood doesn't have a lot of expertise in that area to begin with.
