Also looking for a DD conversion kit, but want the canvas in upright position. Searched the web, but it seems I have to do some scratchbuilding here.
Here are some useful links to the Sherman DD:
http://www.d-daytanks.org.uk/tanks/sherman-dd.html
http://perso.wanadoo.fr/cap.info/ddtank/nat-archives/archives.htm
http://afvinteriors.hobbyvista.com/dd/dd1.html