Maybe this modification is already well-known, but in case it isn't, here's a suggestion:
![](http://i.imgur.com/t2820Hq.png)
That tiny little nick filed into the can opener's edge hook helps the edge hook hold onto the tiny curved seam around the bottom of the can lid. It doesn't look like much, but it makes a significant difference. I used a triangular diamond-grit jeweler's file to do the work.
Years ago I had a P38 can opener which, being made of cheap soft sheetmetal, developed this same nick on its own after just a few uses. I quickly noticed how the nick helped the P38 hang onto the edge of the lid better, and I've made a point of replicating it on every multitool can opener I've had since then.