My DH would NEVER build anything for his wife to ride on because:
We were at a show, and a pony came running towards the barn with a part of it's cart still attached, having had the driver's part break off while trotting across the course. Yes, her DH built it.
We were at a show, and my friend found herself and her cart seat suddenly on the ground. It just broke off. No, it was not home built.
DH spent 1/2 of his time at a show helping the very generous barn owner try to weld a competitor's cart back together where it broke. It was brand new.
I was riding at a pleasure drive in a cart when there was a loud CLUNK, and the seat dropped about 4 inches. Luckily the horse just stopped, we unhitched out there in the field, and a truck carried the cart back to the barn. It was a very respected company's product, but it had happened before.
My DH says there is NO WAY he is building something for his wife to get killed in!! And I would not hitch it to my horse if he did, LOL!!
I don't mean to be a downer, but I thought you might like to have some real life experiences...sorry if you did not want to know!