I'm just gonna leave an analysis of the puzzle along with my failed attempt at start height.

Start Height:
Everything has to start on a line, which means no tri-arms or hex-arms, and probably no min rate unless someone goes really crazy.
Piston arms and bi-arms are basically the only arms you should use. If your bi-arm is waiting long enough for it to become a single arm, you’re probably not doing the metric right.
Tracks are mostly useless except for waste chains, you would probably rather have an extra piston there or just remove the track and shift everything else closer.
I’m willing to bet the min rate solve with 1 start height is either 6 (bi-arm loop) or 4.01 (crazy almost-min-rate epsilon).
All arms have to have at maximum 5 tiles of space in between them, unless you are always dealing with bonded molecules in transfer between these. The most efficient transfer happens with only 2 tiles of space between the two arms, but usually isn’t possible.

Latency:
Min latency is 7, not using division. For Leaden Sea, a copper water and copper air go through three rejections, then bond to each other, then release their air, then output. For Star Tide, the copper air projects twice and bonds to an copper water and then outputs.
Division is not minimum latency because it has to waste a cycle debonding one of the inputs, and on top of the missed latency from that, division has lag too.

Some primary metrics feel more like restrictions than things to optimize. This is the case with both of these metrics. You are optimizing for the minimum cost while still having 7 latency, tiebreakers via area. You are optimizing for the minimum cycles while having everything start on a line. There are things like LexC, where if that is the first metric, you are optimizing for LexC, ties broken by whatever. Cycles, you are (in some cases) optimizing for cycles, ties broken by something and something else.
What I’m basically saying is that some primary metrics are more like restrictions, leading to more ties in those metrics due to less tiebreakers.
However it seems like a lot of people didn’t do the latency calculation, so maybe that doesn’t quite qualify as a restriction. For a while I thought min latency was 8, too.
