17R Playtest solve, made entirely pre-release (apart from rotating the input because the pre-release version's input is flipped). Optimised version of my first solve.

16R is both possible and likely easier than this, by purifying everything in the input chamber. That method caps out at 16R though, where I expect a pileup at the top end.

I instead shot the moon with an input chamber that can easily support 14R, but couldn't make the output chamber work so you get a 17R instead. With the two empty spaces that I couldn't make use of, I reckon sub-16R is possible but it might require something special.