gmferg,
We followed your idea and mounted the "fence post" under the porch on our Trailmini against the rear supports. Love the storage capability and being able to have a real sewer hose instead of that tiny flimsy one. It is far enough back, that we are careful when backing into the driveway (close clearance - 2").
Our "old" storage tube is really short, so its become the extension cord and propane hose storage tube.
The new Sport Deck version of the Trailmini comes with a bumper for storage like the other models. We considered having one installed at the factory but, it makes it overall longer and too long for our garage.
Thanks for the inspiration and construction advice!