18 was a good number : it was the average number of submissions each week.
With the switch to GT4, more drivers will join (even if they don't race on a regular basis), so I extended the points to the 20 fastest times, for each division, so that's a total of 60 drivers who will score points each week.
As for an overall board, we experienced it for 7 or 8 months, and the problem is that div 2 and div 3 drivers will never reach the top spots.
It's kind of frustrating to give your best every week and still stay between 5th to 10th position on the board while the new fast driver jumped on the podium after 4 weeks (and wins) only.
Having one board per division will be much more rewarding since div2 and div3 will also have their own podium.
Points will be carried though when someone is promoted, so that they don't have to start from the scratch again. And that's why the point distribution is different, so that the top div3 driver promoted to div2 doesn't reach the podium immediately.