Does Guinsoo's extra on-hit procs apply to Runaan's secondary bolts?

I have a question about the interaction of Guinsoo's Rageblade and Runaan's Hurricane. I know that Guinsoo's stacks only on attack, so does not stack on the secondary bolts of Runaan's, but does the double on-hit proc on every second attack apply to the secondary bolts of Runaan's? I have looked around online and cannot seem to find a definite answer. Has anyone tested this, or is anyone sure of the interaction?

Edit: If anyone else doesn't know, but is curious, please comment to keep this post visible in the hopes that someone knows. ;-)