Show more than three recent applications in Dock
I was looking for this myself. It took some digging and experimenting, but I figured it out.
You need to add two keys to your com.apple.dock.plist: show-recents and show-recent-count. Adding show-recent-count alone won't work, even if it's enabled in preferences.
defaults write com.apple.dock show-recents -bool true;
defaults write com.apple.dock show-recent-count -int 10;
killall Dock
And the results:
Cheers!