As this thread has been revived...
I like the idea of speed-stringing fish onto my float line (although as Marwan said, it could get unpleasantly fishy) to avoid having to retrieve or return to my float. However, I don't like the idea of detaching my speargun from the floatline - especially when dealing with a fish. Also, I find those big game Orca clips awkward, sometimes painful, to open. I wonder if the basic speed-stringer set up could be improved upon?
Miles already suggested a lanyard that moves the spike up the floatline a way. I guess using a different type of clip/caribiner solve the Orca problem.
Is there a way to spike the fish onto the float line without the gun ever being detached from the float-line?
Perhaps some kind of 2-point attachment system would be required. Also, I recall seeing, long ago, a device used on yachts that allowed a cable (a safety line to the yachtsman I think) to somehow pass over junctions in the main cable rail that went around the boat while the safety cable always stayed attached.
[Spaghetti, dinner tonight: fresh, grilled sardines to start, followed my meatballs & pasta
. BTW most of our Baked Beans are Italian now -- surely Italians don't eat baked beans?]