usually, the x rounds is under swiss pairing system to get a ranking list.

From the critical last one round, need to decide on the number of positions for up and down before : --

(1) up and down by maximum 1 position with : -- (coming 2010 Group A likely method)

1 vs 2
3 vs 4
5 vs 6
7 vs 8
...

(2) up and down by maximum 2 positions with : --

1 vs 4
2 vs 3

5 vs 8
6 vs 7

...

(3) up and down by maximum 4 positions with : --

1 vs 8
2 vs 7
3 vs 6
4 vs 5

...

2009 3rd “芳庄旅游杯”越南象棋公开赛 used up and down by maximum 4 positions for positons 5 to 12 with (9 + 1) system : --

5 vs 12
6 vs 11
7 vs 10
8 vs 9

You may read below : --

http://v15.huasing.org/sForum/bbs.php?B=123_11366782