I have a Toledo from the sixties and its sound sure kicks ass but when I crank it I'm accompanied by loads of screeching feedback.

If I put some cotton inside it will it stop the feedback without affecting the tone?

I dont want to completely stop the noise though so I wouldnt be completely stuffing it, just enough so I can play louder at band practices.
ya i would agree with the guy above but hollowbodies always get tons of feedback don't they?
Fender American Special Telecaster
Blackstar HT-5
Wren and Cuff Tall Font Russian
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Have you tried standing as far from the amp as possible and facing away from it?
This space foreclosed, due to the ailing economy.
Feedback at high volume/high gain has always been an issue with hollow bodies. It could also be the old pickups that are in it. If they arent potted right or potted at all they can become microphonic and will just make the feedback that much worse.
Billy Duffy used to stuff foam padding into his White Falcon to kill the feedback. He'd put black electrical tape over the foam inside the body, so it wouldn't show. Didn't seem to hurt his tone really...saw them a couple times back when he was just using the Falcon, and it sounded great.