[Amps] GS-35B Vertical Mounting & Input Impedance

[Mike]

Hello,

Is it okay to use the GS-35B in an upside down, vertical 
position?  Want to make final adjustments to the input pi network 
while the tube is operating.  Unfortunately, the tube's grid 
compartment is not easy to get to when the tube is in the operating position.

Also, understand the typical impedance for a single GS-35B is 30 Ohms 
which comes close to what I expect based on the anticipated operating 
values of: Eg=30V, Ip=0.8A & Ig=0.2A.  However, input impedance 
values from 100 Ohms to 25 Ohms have been found in the 
archives.   Anyone have a smaller range of possibilities found from 
experience?

         73,
         Mike, K4GMH