What is the minimum and ideal size for a rookie team?

[yarden.saa]

I have expreianced many problem with my team as a rookie team:
to the competition: 8 members max/min
2 drivers
1 human player
1 coach
1 battery man (charging the batteries)
1 member that is incharged on the electrinics
1 member that is incharged on the mechanical
1 member that is incharged on the robot program
to the build season: 5-6 members is enough

But....
there is a low precent of members that are active members. not every member will be active as the team need. when the team is small the efforts are bigger.
our team was at first 25 members, at the competition we were 16 but 8 were active, the other passive.

It's a big problem in our team that we are still in it, you have to consider it that if your team is too small you can't run it