Well, I think I would have continued the design anyway, partly because of that awful hitch that clamped onto the rear triangle. But yes, the progress may have been slower!
That is one thing I considered, and I actually cut out a flat piece of plastic to extend horizontally forward from the trailer within probably 5mm of the rear tire. That lessened the spray, but did not eliminate it. A vertical wall could work in the right circumstance, I think, but I already have the axle block there to keep my bins from sliding forward. It might prevent me from hauling odd sized stuff for half the year, though, because winter.
Soon I'll be taking my truck's (rusty) wheels to the powder coater, then to the tire place to get new tires mounted, so I'll try to remember to get a picture of that. Last time I hauled wheels/tires it was quite a big job!