What size should a church planting team be?

From From Seed to Fruit, The Gathering of Teams of Laborers, page 141:

Fruitful Practice #2: Aiming for a Large Enough Team

This implies that team size matters, and it does. The average team size of
consultation participants was nine adults (the number being raised by a few very large teams) although the majority of teams were less than nine in size. Team size in itself is not the key to fruitfulness, but a survey of the teams represented at the Consultation indicated the following:

>> Teams with fewer than four adults showed a greater probability of
not planting even one fellowship or church.
>> Teams with eight or more adults had a greater probability of
planting at least one fellowship.
>> Teams with twelve adults showed a greater probability of planting
multiple fellowships.

It would seem, therefore, that if our desire is to see church-planting movements, we need to be aiming for larger numbers of laborers in each team, supporting the strategy of sowing widely. Research suggests that five or six team members should be the lower limit of a team size.

Thoughts? Counter evidence?