ND6T AGC question

Mharpen@...
 

I would like to drive the AGC board with 12V not 5V and assume this involves changing some resistor values. The voltage divider which biases the FET Q2 appears straightforward enough, changing R3 from 100k to around 380k.
The biasing circuit of the amplifier Q1 is more subtle. Changing R2 from 1K to around 2.2K (which seams reasonable) will reduce the slope of the load line, increasing the voltage gain of the amplifier and modify the behavior of the AGC. On the other hand, leaving R1 and R2 unchanged and increasing the voltage from 5 to 12 retains the voltage gain and relocates the quiescent point near the center of the new load line, where it should be. Am I wrong to assume that the only change needed is the value of R3? 
 
Comments please. Mike N6CMY 

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