Looks awesome! man, I'm getting ready to do the same thing to my barrow as soon as all the parts get here. Who ever thought one wheel was good enough didn't think about it to much. One thing I might do is put another brace next to the metal piece in front cause I like your other two you put on. What size tires are those? Good job man, your hired.
When you say those dolly wheels are too small, how small is too small? Ive got 2 harbor freight 8" wheels. Im thinking either cut the front end of the handles a little shorter or move them more toward the front
The only reason I didn’t use the small ones was because I would have had to move the brackets or shorten the end like you are saying. But the bigger the better. A bigger wheel will roll over small bumps and rock much easier and smoother than a small wheel. Either would work. I’d say try it with what you have and if it doesn’t work really well then go get some 10 or 12 inch ones.