There are better ways to reduce feedback.
Use less gain;
get a longer cord;
don't face the amp, keep it behind you and if possible keep some distance;
good quality, wax potted pickups.
I didn't use any gain, it's a non MV Princeton Reverb Reissue, on FULL!
No point in that, there was 8 of us and nowehere else I could of stood
See below
The pickups have been rewound by hand and properly potted
The tape is for body feedback as opposed to pickup squeel. Without the tape it is uncontrolable but with it you can just let the body resonate when you want to. I did face away from the amp most of the time but occationally I turned round so the guitar was about a foot from the front of the amp and just let it howl whilst holding the chords, it sounds very musical.
Ultimately, I'll go back to a Tele and use some pedal gain but it was nice to use a hollow body straight into the amp, but the tape is a must!