I have rebuilt several Holsclaw steel trailer. I change out the 16ga. or 1/16" with 11ga. or 1/8" thick steel tubing on the cross bar and I also replace the tongue steel with 1/8" steel. I add length to both the cross bar as a step and I add several feet to the tongue tubing so that it reaches further back almost to the axle and with another 2 foot out front. This improves balance with an heavy loaded trailer.
To reach back further through the trailer, I cut out a "window" in the original channel where the front tubing terminated sending the new longer steel tubing through that window to the next channel and bolt it there. This stiffens the whole trailer. I add a pair of angle iron "cleats" to strengthen that channel that I cut the window in.
I live in Indiana ,so most trailer are steel and not galvanized. Galvanized is a better product all around.....