Yaesu FT-840 - Reduce Minimum Power
 

I use an FT-840 and would like to add an external 6 meter transverter.
The problem is the FT-840 puts out about 10 watts at it's lowest power
setting. My transverter is designed for 5 watt input maximum.

Does anyone know how to adjust the radio for a reduced minimum power
output? What I was hoping was to reduce the minimum only and try to
keep the maximum output settings to 100w.