I recently upgraded my 6:1 triple stack to 7:1 by adding a Harken Mini-Block and stand-up spring to the eye strap and then running the free end up to a spare boom bale as recommended in the Parts and Accessories guide. I am not entirely satisfied with the results. The problem is the mini-block doesn't swivel and thus doesn't stay aligned with the boom when I have the mainsheet system sheeted in hard and pointed towards the hull. Essentially, due to the twisting effect I don't feel like I'm getting anything out of this upgrade. If anything, it's more of a "downgrade" because it's become harder to cleat my main (which wants to point forward due to the torque). The problem is compounded when the wind is up. Any suggestions? I see a Swivel Shackle listed in the Connectors section of the guide but I'm concerned the clevis pins might not be ideal with the stand-up spring. Ronstan sells a similar shackle without the clevis pins (Part #183322)
Here's a picture of my setup....