Well I go with what MS says but I couldn't find your link. What frustrates me is sailing ropes aren't rated for shock in any way like for instance a climbing rope. So stronger but lower stretch may be more vulnerable than an old bungy cord.
I don't think MS has opined on line size and block size. The link is just a link to his forum.
Most lines on a sailboat are not subject to shock loading. Most are subject to a constant strain or tension. The most vulnerable lines to shock loading are the traveler control lines, mainsheet, jacklines/tethers, and spin sheets.
Drew Frye has done research on using dynamic climbing ropes for travelers for Practical Sailor, he may have posted some of the info on his website (
Sail Delmarva) as well as on PS. He is an occasional visitor to SBO and posts under Thinwater. Search his posts to see if he has written anything on this.
One issue with testing line for shock loading is coming up with a standard. It is pretty straight forward for climbing ropes, drop a specified weight a designated distance and see how times it takes to break the line. Climbers also count the number of times they fall, I don't think sailors count the number of accidental jibs.
The issue for shock load testing, I would think, is coming up with a standard. The shock load in an accidental jibe in 10 knots of breeze is going to be much lower than in 20 knots. I suppose there a standard could be developed but how would a sailor evaluate it? In climbing the falls are counted and the rope retired at or before the rated number of falls. It is also pretty easy to know the forces involved. The climber knows his/her weight and the distance he fell. Without some sort of load gauge on the rigging, how would a sailor know how much force was exerted in an accidental jibe?
I have been intrigued with the notion of using dynamic climbing rope for the traveller. Unlike a halyard, static stretching is not much of an issue for a traveller, and unlike a traveller dynamic stretching is not an issue with a halyard.