Weircliffe Bulk Tape Eraser / Big Electromagnet - Modification / Butchering

I modified an old bulk tape eraser so I could use it to demagnetise larger tapes, or indeed anything that needs to be demagnetised.
Some might call it modification, some might call it butchering. The mean spirited would call it a bodge!

[@SDsailor7]

How many pases do you give a 7 inch tape reel to erase it on both sides?
Thank you

[@estudiospatagonia5636]

Work with 2" tape?