I like the tape marker idea. "lasts at least a year" -- I fully expect my RA line to last a lifetime, it will probably be passed down for generations
. I'm only half kidding.
Re. polypropylene being stiff & knots coming loose.
Splicing is cheap, neat and relatively easy: loosen the three main threads for a couple of inches (5cm) and
melt the ends to stop further fraying, then use a pencil/spike (as a "fid") to help open up gaps in the main length of rope (bight?) and then just weave the three ends back into the main length to make the loop. I tidy the result up by melting off any stray fibres and the 3 ends again, flatting them to make it harder to them to pull back through. The RA floatlines come prepared with a spliced loop at each end, so I
expect this method to be very strong.
[ame=http://en.wikipedia.org/wiki/Eye_splice]Eye splice - Wikipedia, the free encyclopedia[/ame]
Alternatively, you could bend each end over and
whip loops in the ends with whipping cord, which again would give smooth, finished result. I would also super-glue over the whipped length. This
might not be strong enough for large fish*. The length of the whipping, the type & size of cord used and the quality/tightness of the whipping would likely be factors affecting strength. I would whip about 1-2", perhaps more for bigger fish, and melt the ends to stop them fraying and make it harder for them to pull through
[ame=http://en.wikipedia.org/wiki/Whipping_knot]Whipping knot - Wikipedia, the free encyclopedia[/ame]
*Note whipped loops are used in flyfishing and this articles suggests, in that context at least (e.g. thin, mono lines), they might not be suitable for larger fish:
"Whipped Loop
...However, even though many anglers swear by this connection, it is not nearly as secure as the monofilament nail knots, and I have seen a number of these loops pull free. I do not recommend this system for large saltwater species."
Alternatively, you could even
crimp loops like in spearline - good luck finding the right size crimps though
.