your Rockwood has an ultra-lite frame and that, along with the weak bumper welds, are an accident waiting to happen for what you want to do.
some owners have a receiver welded and braced to the frame and bumper, for bicycles. but this mod will usually void the frame's warranty. if the warranty is up, then you can do what you want. but ultra-lite frames are designed for the types of weights you're talking about.
but you should call the frame manufacturer and get their input.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC