Just a quick update. Received a 5L flask for my birthday. The thicker glass made it hard for my original setup to couple to the stir bar very well. I added a pair of disc magnets I had laying around to the top of the hard drive magnet. In the initial test the magnetic force lifted the fan (and the padded insert it was glued to) up to the top of the enclosure rendering the fan unable to spin
added some more hot glue to keep everything where it should be and I can now pull a vortex to the bottom of the 5L flask should I want to.
Here is a pic running at 9 volts, it is hard to tell from the pic but everything under the krusean is swirling around nicely.