I was afraid of this

i had an article planned to show you the correct way to mount a porch or addition to a trailer.

You really can't have the trailer holding up part of an additional structure.
In a house, this is normal. Just attach a stringer to the wall, and build a porch.

In a house that is the strongest place. There is very little you can do to hurt it.

In a trailer, that is the weakest place, and there is almost nothing you can do to reinforce it.

So, additions need to be their own structure. A self supporting box, and you put an expansion joint between the two structures.
Usually this folded cloth, or an accordion type stuff.

Sorry i never got to the post