I owned a similar trailer in the past. My only suggestions are to replace the garbage castors that bolt to the trailer with better quality ones and weld them on... it makes all the difference because the shitty ones that come standard fall apart when the balls fall out. I always considered welding the rest of the frame but never got around to it and just sold it and bought an enclosed trailer instead.
Also, being chinese steel... these rust. Make sure you stay on top of the rust with some wire and spray paint.
Do the wires get pinched when you fold it flat? I remember my trailer rubbed together there along the two halves.