This reawakened thread seems the right place to relate my latest Carradice repair. After a 15 years of everyday commuting and annual tour my Super-Cs were in dire need of some patching. I bought 2 patch kits from carradice which include several swatches of cotton duck canvas material, a tube of copydex rubber cement/glue and advice on shaping patches for corners..
Tips: gluing on extra layers can create a stress raiser along the edge of the patch. Avoid straight lines in your patch by cutting a zigzag pattern (like pinking shears but larger), rounded corners and wibbly-wobbly patch shapes.
I reinforced the worn top edge of the pocket with a wrap-over patch but created the foldover halway along the patch. I now have a stress raiser going from 1 layer to 3 layers. Ill have to rip it off and reshape so the inside and outside parts of the patch dont match up.

In normal use you can find wear lines, eg on flap-tops from buckle to edge. Gluing a patch across part of this line may help reduce the stress line and eliminate or shift wear.