I read today on an English board adjusting the position of a hop bag inside a keg or fermenter using magnets. Sounds like a great idea. I recently dry hopped an NZ IPA with 110gm (5.5gm/lt) in two muslin bags. Despite weighing down with glass weights they still floated half in half out. I can see that the magnets will take the guess work out of the weights, i.e. too little and they'll float, too much and they'll sink to the bottom and get covered in trub. Would also solve the problem about dry hopping in a fermenter. Dry hop for a week or two then just slide the bag up into the ulage space before it starts leeching tannins.
The writer recommended neodymium magnets which can be small, but extremely powerful. I understand that they are nickel coated, so should be OK to immerse. However they are so powerful that they can apparently chip or shatter if you accidentally let them clash together...maybe another type would be more suitable?
Has anyone tried doing something like this?