The snap shackle in the photo you posted should work OK. We got rid of the snap shackle and just use regular shackles to prevent 2 blocking at max rake (we use the Harken 75mm bottom unit). If you are using the 57mm units or equivalent you should be able to use the snap shackles.
The S hook looks nice - but I wouldn't trust it in a distance race - especially when Jesse has bust open a can of spinach...
Chris.
