Fixed in the new Developer release (33.0.1963.0).

It's a portable installation. The switch is probably the best way to go if I can't create a location where the plugin will be recognized without it.

Is there a location on a portable installation that I can put the pepperflash plugin where it'll be read? I'd like to avoid pointing to it by the command line if at all possible.

Is there any way to get rid of the unnecessary "+" at the left on the bookmarks bar?

"Allow in private mode" is there on the extension page. Check it if you want them to work in a private window.

"F:\Program Files (x86)\Opera\launcher.exe" --disk-cache-dir=E:\Cache

Try it with quotes only around the Opera path.

--disk-cache-dir=E:\Cache

Developer build now contains the Chrome .pdf plugin that recently went open source.

"C:\Program Files (x86)\Opera\launcher.exe" --disk-cache-size=50000000

That should limit your cache to 50MB and you can alter the size to your wishes. It's a Chromium switch and should work, but no guarantees.

Pass it to opera.exe in a shortcut.