Home Distiller

Big ass corks are great. I have heaps.

if you were set on using cheese cloth you could soak it in melted beeswax to get a better seal. Even when set it remains soft ish (unless freezing!)
It would also remove it's wicking potential
I like the faint hint of honey it gives to my vodka - i dip my corks in it.

That seems excessive. I think I would use the cheesecloth method for a month or so, then go back to the rubber seals for longer term aging. I do not think the rubber seal would that much of a problem if no contact was made of the whiskey itself.
Good luck

BG