The Picture of a restored Lycett saddle in the "Lycett for Nortons" part shows an incorrect configuration of the saddle elastics. Based on an original saddle mounted on a WD16H in March 1939, there should be short elastics at the side and long elastics in the middle as can be seen on attached picture. This set-up is also visible in the BSA and Triumph saddles.
Comparing the measurements based on this saddle and the lengths in the VAOS of the period it is shown that the elastics did not have identical elongation values (pre-stretch), being approx 15% for the short ones, 19% for the middle ones and 9% for the longest ones in the original configuration. These values are only valid for the contemporary (1936 to 1941) elastic chords. The elastic chord presently coming from Czech Republic appears to have a much higher modulus meaning they need much more force to obtain the same elongation and are thus to be longer than the original ones to have a lower pre-stretch to get a comparative similar in situ support function. Unstretched lengths of the Czech chords need to be resp. 344, 443 and 494 mm to start with. How much pre-tension one wants can be determined by oneself. Will add some more info on the www.wdnorton.nl website in the future.