Lowering router transmit power after 9dbi upgrade

[kitkat12012]

I had just bought a pair of 9dbi antennas for my wrt54gl

I read somewhere that I should lower the transmit power when increasing the antenna's gain, although I'm not sure what to set it to.

I'm currently using the tomato firmware and transmit power is still on the default value of 42.

I need some suggestions on what to set this value for my new antennas.

Thanks