For my Pfaff I use plastic bobbins specifically made for Pfaff. They are smaller than the ones I use in my cheapie Brother. I also use prewound bobbins in echu or lt. grey that have thin cardboard bobbins and never had a problem in either machine. I also have some old metal bobbins that only fit in the Brother, but sometimes they do rattle a bit. For my Feathweight I only use the bobbins that came with it.
Liked the idea one gal had to use up small amounts in bobbins on the top, that's what I do when I make string quilts.
May in Jersey who hasn't touched any of her machines in a long while and is getting withdrawal symptoms, LOL!