On the issue of trailer STRENGTH.
It is true that very few of us carry more than 1000lbs of weight, but gross capacity is not our biggest problem.
Trailer FLEX is.
Because of the length and center of gravity of our boats, our trailers are very long.
This length causes a great deal of both vertical and lateral flexing while traveling.
The welds and the area around them are especially susceptable to damage from flexing.
I have repaired several of my trailers and helped fix others.
We need STIFF trailers.
If I were building a trailer from scratch, I would make the frame as large and long as possible and add reinforcing plates at the welds.
And have it dip galvanized.