Re: Asymmetrical Spi & Foil Headstay
As long as the load is spread out on the forestay a bit, which the commercially available "tacker" type products do, you shouldn't have a problem. Where you might run into a problem is if you just used a piece of rope or webbing, or if you had excessive slack in your headstay.
I'm not a big fan of that setup, but many people do it.
1979 Santana 30 Tall Rig