dual triode - single, parallel, series switch

[camerasteve]

first of all, thanks to everyone here that i learn't from as i built and messed with my 5e3.

i have changed it to a single channel amp and would like to use a rotary switch on the first 12ay7/12ax7 to go from - single triode, parallel and series operation.
my stumbling block is what to do with the unused triode when in single mode.
do i need to ground the grid like the standard imput jacks do?
disconnect the grid?
disconnect the plate?
disconnect the b+ supply?

i intend to separate the cathodes (i presume i have to)

if someone could point me towards a schematic that switches a triode in or out of the circuit like this i would appreciate it.

cheers

by the way, whats the difference between cascade and cascode?

[Tubenit]

triode switch

Ground the grid when not using the triode.