Turns out going through the top at the beginning is like 1s faster than going through the bottom. To avoid the first enemy doing the first pogo nil is more than good enough (the 2nd one is only for speed).
I thought it'd be a good idea to lab so good harpoons to be able to compare them against other potential good spots. The harpoon in the middle of the room saves roughly 1.1s and the one at the end saves roughly 1s, so both are very good