[Amps] Grounded Grid(Screen) 4CX250B power gain

[Hsu]

 Hi, 
 Anyone have experience in grounded grid  a pair 4CX250Bs amplifier? could you tell me how much power gain of this configation?
   This weekend, I'm planing to do a tube conversion in my friend's Henry tempo 2001(a pair 3CX400A7),I have give up GI-7B due to its
 larger volume.The only choise is 4CX250B.The gride driven configation needs screen and grid power supply,so I want to  use G-G configation
 (gird+cathode as cathode,screen as grid,  due to the 4CX250B   grid's few power rating, it is low mu triode now).
 But I don't know its exact power gain,anyone can tell me about this?Thanks in advance!
      73!
          Hsu