I built a trailer something like this, only a little bigger, I pull it with my mower or my 4 wheeler, bed is 4 ft X 5 ft axle is just a little off center so it will dump, I think I moved the axle 6 in. forward of center, I used 22 x 10 x 8 tires, they don't make any ruts in the yard, one thing you need to watch out for is the trailer has to be high enough off the ground so the bed can dump, my trailer has a good steep angle when in the dump mod, I didn't build my trailer with steel plate, I built a my frame with 1.25 angle iron & used treated 3/4 ply wood, it's over 10 years old and still going strong, it is light enough to move by hand, & strong enough to do any thing around the place
Rat
I don't know how to post pictures, if You would like, I could take a couple pic. & email them to you