Have a look here for the initial settings:http://www.heilsound.com/amateur/support/dsp-settings/all-things-yaesu
My own rule of thumb with studio type microphones-(Although the PR781 is tailored..), is roll off some of the low Bass frequencies, below 100 to 200Hz.. Lift the mids-1.2 kHz+ slightly and lift the Highs. Otherwise it might sound dull and 'muddy'.
Although we all hanker after the "ESSB" sound, over processing the audio within a limited bandwidth can make it sound terrible!.
I found with my TS-870s the best setting was no processing, no EQ. and high boost. (SM8)
The IC-7700, I use some processing, and lift the highs slightly.(PR781)
Experiment over the air with some stations that are familiar with your voice, just remember with 10 stations you might get 10 different opinions!.. I normally use good headphones and the monitor facility (into dummy load) to start with before getting over the air opinions.
73 de William
ZS4L / ZS5WC