I stumbled on this stupid-simple build that will kick out extra U-235 with splitter priorities instead of using chests and circuit counters.
It takes a bit for it to "settle in" and may kick out some U-238 during startup. Probably not an ideal build for early game as it takes quite a bit of uranium to get belt "back pressure" correct.
Grab a deconstruction planner and add it to the filter of your merge splitter so you don't get any output on the one side. (edit: whoops, I see the ones at the top are filtered, I was talking about the one on the left)
For me, not blocking the output of a splitter is a personal note/habit that the splitter can be moved or should be moved later. (Having the wasted materials sticking out is annoying as hell and it will tickle a few neurons when I am scrolling around older or more complex builds. Basically, it helps me remember any earlier intent.)