This halyard system is the best performing system available. Made by our in-house riggers here at APS, we start with 1/8 in Yale Vectrus 12, which has no stretch, runs smoothly, and has factory applied clear Maxijacket coating to prevent UV damage and reduce line damage due to abrasion and wear. We splice on a KB6 Karver block (extremely strong) to one end. The block's design allows the line to be run around the center of the block prior to splicing. We then whip our splice to keep things tightly in place.
Now the Vectrus 12 is run through a Harken Hook-in block (EX1351H), which provides the best fit against the mast available in a block due to its contoured shape. On the sprit end of the line we use the lesser known brummel splice that cross braids the Vectrus 12 so the fibers are effectively locked and can's pull out. Additionally, we whip the splice to keep things tightly in place. To prevent the loss of the Harken hook-in block when the system is not in use on the boat, we position a black rubber grommet so the block does not slide off.
You won't find a better sprit halyard for your Optimist!