For me size was a factor of my one design class so I am not sure it is directly applicable, however ISAF rule 3.14.6 "Lifeline Minimum Diameters, Required Materials, Specifications" requires a vessel 8.5m-13m to use at least 4 mm (5/32 in) wire. If you size your lifelines based upon breaking strength you would need to use the same size Dyneem (use amsteel blue for this application) as wire (the rope has a slightly higher breaking strength than the same size wire). Personally for a cruising boat I would probably go up another size or two depending on the size of holes I have in the stantions, but I can't point to a good justification for doing so, other than bigger is better, and the strength goes up significantly for each additional mm of diameter (4,000lbs for 4mm, 5400 for 5, 8600 for 6). Check out Samsons website at
http://www.samsonrope.com/site_files...0_Catalog_.pdf for more information.
There may be other acceptable splices for this stuff, but I used the splice from the manufacturers website at
http://www.samsonrope.com/site_files/12S_C2_EyeSpl.pdf . Took me about an afternoon to do the entire boat, though I am sure If I had had either more or less beer it would have taken less time. I am trying to get out to the boat to take pictures, buts it has been a heck of a weekend.