My post was waiting to be moderated, so it didn't appear until a couple hours later.
By the way, I've added an option to turn the "error bars" display on and off. (It's on by default.) I think all the important options are exposed now.
The next problem I'd like to solve is that I've got 15 of these blocks running in parallel to decode a local trunked radio system, and so I'm often hearing multiple transmissions at once. I was thinking of making a GNU Radio block that would buffer the audio when multiple channels are in use, and play back the buffered audio during the gaps when no channels are transmitting.
Also, I'm interested in decoding the control channel so I can hear only certain talkgroups (and eliminate the need to have 15 channel filters and 15 gr-dsd blocks constantly running). It would be great to have a GNU Radio block for that. Does anyone know the best open source EDACS control channel decoder is, or at least a description of how to decode it?