I have sneaking suspicion that there are multiple solutions to this, because that felt way too easy (granted, not trivial, but the first thing I tried worked) for a level that looks this intimidating (this has 4 holes, levels with 2-3 holes have given me trouble).
A quintessential "pipelining" level in my opinion. Dry, exceedingly logical, but requires a decent amount of effort to actually understand why the solution is shortest.
Edit: 3 distinct classes of solutions, each with small timing variations.
Insights