I know Frank at Fishman is good at responding to questions and such. He was quite helpful with me when I was first deciding on how to equip my Avalon.
I primarily used my Lowden for worship yesterday. But I did find time to do a little bit of experimentation with the Avalon.
My first step was to remove the outboard effects from the circuit. I suspected that the Line 6 POD's compressor was contributing to the problem. My findings are certainly not scientific, but, I was able to play the Avalon without feedback, even with the mic pointed at the soundhole.
I'll be playing around with this in coming weeks and months, as time allows. The church I'm serving at is 220 miles from home, so I spend what time I have working with the worship team.