Absolutely!
Make all the tables seat six. Then, on whichever one you would like to be the final table (from the tables tab), right click, and select "add new seat" twice. Then, right click to make two seats be unavailable (I'd recommend seats 7 and
. Or, create the tables needed of six each, then make a new table of eight, and right click to make them all be unavailable, until you are down to eight. I would suggest my first option, as that would be less work. A third option would be to insert two new seats once you are down to eight or nine players, which may be less work, but would require you to remember where you are in the tournament. First two options you could set up before registering players, if you so chose.