Ah, nifty. I think one will do without, and just not create a total seal at the top of the reflux column.
The reflux column is almost ready physically, but needs packing, since the end of the tubes are flush, packing would fall out. Can you suggest a permeable material that one could use to hold packing in there that won't affect an al/hg rxn?
One could possibly dream of putting aluminum mesh like kitchen seive wire over the end...?