dimensions of talon

I am new in this great forum and I read nearly all subjects concerning to valve making and all projects done here.
i found an alluminum tube that used in a photocopier .Its ID is 21mm with a wall thickness of 5 mm and overall legnth of 40 cm .
Also I got a diana 50 barrel (about 17 inch) 0.22 caliber .
I want to make a Talon or Condor with velocity of 1000 fps or more if possible and need help about some numbers
ID of valve stem and diameter of valve orifice and also the derlin cap Diameter of the part of the barrel inside the breach
legnth of the open part in the frame that the breach appear from
Forgive me for my bad english
Any advice will be appriciated especially in simple english suiting my bad english
Thank you in advance