This setup was found on a boat that have never sailed with a jib and mostly likely will never be sailed with a jib. It is fully geared towards singlehanded sailing.
Personally I agree with Tim, I too would not have double lines running up the forestay.
My idea it to run it like this :
In words :
I would loose the double block (back to back block) completely. I do this by having only a single block where the double block should be. And I'll tie only a single line (blue) to this block that will pull the tack out. The red line is basically the spi top halyard with the other end being the retrieval line. from the cleat on the mainbeam it will go forward to the single block and make a turn back there. Then it will run through a block just in front of the forestay and up along it. This way only a single line will be there. Of course it will go through another block at the hound fitting and through the block at the spi gate before coming down to the snuffer hoop and the top of the spi sail.
I'm hoping to achieve two things with this setup. First because I have lost the double block the force on the spi tack is twice it was before and it is also twice the force that is on the top of the spi sail. This way the spi is always pulled down towards the pole. Secondly the tack will be pulled out first when hoisting and only when it hits the tip of the pole will most of the spi be pulled out. This is pretty much how crews pull the spi out on boats with a 2-line system. My idea has the same behaviour but now with a single line setup. When doucing the behaviour will be inreverse. A third advantage (hoped) is that when hoisting the spi the red line received some slack then with the old system. About 5 feet more (1.5 meter). So the retrieval line can be made tight on the upwind legs but with the spi hoisted is will very slack allowing to be sheeted out unhampered. I'm hoping this will clean up the trampoline further on upwind legs.
I'm not sure when I will try this setup. I may just have to buy a new top halyard and that is expensive. Otherwise I just have the splice an addition length of line to my current top halyard and lengthen it that way. Maybe something for next season.
Anybody is welcome to try this idea before I do however. As long as you report back with the results.
The basic idea to have the spi halyard run up along the forestay and not the mast is too :
-1- Not disturb the flow of air over the mast. Maybe this helps in upwind performance
-2- Create less friction in the halyard line as it won't rub against the mast, spreader and hound fitting
Wouter