Samson has a method for splicing used line that works easily. It is not as strong as a normal splice, but is likely twice as strong as a bowline so likely strong enough. They basically just cut off the core and don't bother. The numbers work like this - half the load is carried by both a cover and core. Half the load is carried by just the cover. The cover has half the strength so the overall splice should be about line strength. But the line with a bowline is about half the strength of the line so you are better off even with this less than perfect splice then you were with the bowline. I have a copy of the pdf on L-36.com. I think it is on the Samson site as well.
Eye Splice In Used Line;