I had the same problem with my Dean Chafin Del Sol when I played on stage. Feedback was always a problem.
Several different sources suggested that I stuff the F-holes with insulation.
I ended up buying a PRS for the stage, I still have the Chafin but only use it in the studio.
BTW, the sound man had a love/hate relationship with the Chafin guitar. The tone was great but he spend considerable time at each gig trying to move mikes and monitors around to eliminate the feedback.