Rick West's building site has what you are looking for
http://www.ec12.info/building_the_ec12.htmAlso some of the manufacturers sell removable jumper kits. I know RMD Marine has a very nice carbon fiber jumper that is pretty much unbreakable. You can also try CPM.
There are also a number of designs in the EC12 Manual, but it is out of print at the moment.
If you visit the lake with other EC12s, you should find a couple of options to look at. Bring your camera and take some notes.