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.
Yeah, that looks reasonable for late game when you have a surplus of processed isotopes.
I try to set up kovarex as soon as I have the minimum amount necessary to start one centrifuge. I usually build it with only belts, splitters and inserters โ not even logi chests.