I don't know if you contacted Dumas about the rudder,but I did and got a reply yesterday.They stated that their #3507 rudder is 4.5" long x 1.25" wide .Your rudders on your boat if original are also 4.5 " long.Maybe order two so they're matching set. Your hull has been repainted from the original SS version.Here's the email I got and a pic of a rudder on a Shockwave SS.
Thank you for your inquiry. The rudder blade on the #3506 rudder measure 4" long and 1.25" wide. The rudder blade on the #3507 is 4.5" long and 1.25" wide. The #3507 is the rudder we used on the 38 KV. Hope this helps.
Best regards,
Doug