Updated the microsail to have jam cleats, using a split in the wood (thanks @rek). Now it's able to be much tighter.
I've realized that the sail is actually too big for the mast & boom! I cut the fabric to match those dimensions, but to get a really tight-trimmed sail, I think the sail needs to actually be *smaller* than the triangle of space here, so that it can have room when it needs to be stretched.
Sunbeam City is a anticapitalist, antifascist solarpunk instance that is run collectively.