DH>>>     Ooops....  I guess I gotta use a lower value plate resistor and 
DH>>> lower
DH>>>     the gain.
DH>>NO!
DH>>Think for a moment.
DH>>Lower value resistor for the same voltage will pass more current.
DH>>No more tube...
>     By now you've figured out that I've been away from this stuff
>     for a year.  I was thinking of the stuff in the RCA tube manual
>     that shows how to set up the tube for a gain of 20, or 30, or 40, etc.
>     Fender preamp stages are typically set up for a gain of 40.
>     That would probably require some experimental tweeking of the
>     plate voltage to something other than the 45V figure you mentioned.
NO!  NO!  NO!!!
The gain of a stage is *NOT* set by the plate voltage
The gain of a stage is *NOT* set by the plate resistor
Yes - you will be able to change the level of the output by changing
these two parameters but you will also change the operating parameters
of that tube.  When you do this, you will run into excessive
current ( which can make a $20 tube dog-meat in about 30 seconds ),
instabilities and oscillation - generally not musical and generally 
always expensive and wasteful...
Stop playing, dig the book out and spend a couple hours going over the 
examples.  There are only a few components which need to be changed, 
how to figure out the new values can be done in a minute or two with a 
simple calculator ( add, divide and multiply )
HINT:  It has absolutly nothing to do with plate voltage or resistors.
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