I've been trying the same sort of thing recently, using pieces of new self-adhesive felt tabs (
http://www.ebay.co.uk/itm/281170901231? ... 1439.l2649). So far, the experiments have been quite promising, although getting the thickness of the tab correct is the key element. The self adhesive nature of the tabs makes fixing them onto the brass spring easy, and so far, they have stuck nice and firmly.
I've been trying to find out what the composition of 'proper' cassette felt tabs should be, and where to get hold of them. It seems like a waste to have to butcher tapes just to get the pads, but I am conscious that the ones I am using are a little too firm, and perhaps need to be a bit more compressible.
Unpacking a JS-ROM QL, with a QL-SD and SuperQBoard, and busily refelting millions of microdrives