[xubuntu] Change the size of the xfce-pulseaudo-plugin icon

After two years waiting for the Dropbox vanishing icon problem to be solved, when I installed 16.04 I removed the indicator plugin from the top XFCE panel and added Firetray and the xfce4-pulseaudio-plugin, and all is mostly well. The Dropbox icon appears in the notification area and Firetray does most of what the message indicator did. The catch is that the icon for the xfce4-pulseaudio-plugin is too big, as you can see in the screenshot.

audioplugin.png

This is not a huge problem, and it's not nearly as aoying as the Dropbox problem is. Still, is there a way to make the audio plugin icon smaller? I messed around with it a little bit, trying to change the icon listed in the .desktop file, but that didn't work. Got a file not found message.

Any help would be much appreciated.