It seems like the result of side-loading a red belt with a compressed yellow belt depends on how the items are aligned. In most cases only one lane will progress onto the red belt, however, using circuits to align the lanes we can achieve stable 100% compression of one red lane.
In the attached save only the right lane on the yellow belt should be able to progress. To make both progress:
- Turn on the south combinator and let the north belt drain
- Turn on the north combinator
- Turn off the south combinator
- Turn off the north combinator
Before
After
