813 tube tc coil

Hi all
I've asked about te wiring of a tetrode or a pentode in a tube TC coil
and Someone Have me  suggested to tie the three grid together, but in te
triode connection of a tetrode or pentode, te tube will not run at full
plate rating voltage (for 813 =2500V)
is better to tie te last grid to te filament (dynamic connection), and
the screen grid appropriately connected by a resistor (in general
variable to fix the oscillator plate current), at rated grid maximum
voltage. The reason of that is that in Italy is very difficult to have a
power triode for a cheap price, I've read in USA for a 833A a price from
20 to 50 USD; in Italy if you have a good luck to find it, you have to
spend about 150 USD or more.