I feel your Pain my Brother.
A Harbor Freight Frame is an Ugly thing!!!
I have done it a few ways. The first is to Narrow the frame by 1" or 1 1/2" so as to let your outside materials cover it.
The second is to embrace the frame....let it become one with the Trailer.
And what ever you do....get rid of that "Step-up hitch coupler" its a dead give away.
No one will ever Know!
But after the fact....drop back and punt!
Happy Trails
Len