MOD102+ amp build mod question, cathode bias resistor/cap values

[ShadSunsCrash]

Im about to start my MOD102+ build, its actually a MOD102 but i have all the extra parts to make it a MOD102+ along with some other components for some mods im going to do to the tone stack as well. The main question i have is about the main output section mod I want to do. What im planning on doing in the output section is adding an octal socket to run the stock EL84 but also a 6V6(one at a time never both at once). I plan to do this with a switch that lifts one tubes cathode resistor/cap at a time. And all the other connections will be in parallel to their respective pins.

My question is what should my bias values be for the 6V6(for the cathode resistor and capacitor)? The best i could figure is 470/5W and 25uF but that was only based on what similar single ended amps with a single 6V6 use (fender champ). Im trying to figure out how to do the calculations but failing miserably. Below is the schematic with the voltages, and i guess ill post the layout for good measure. Also i know that ideally a 6V6 would have a higher input from the preamp but i can live with a slight volume mismatch when going from the EL84 to the 6V6, that or i could attenuate the EL84. From what ive seen of other similar mods the El84 needs the volume to be on 7-8 to match the 6V6 with the volume all the way up. If anyone is able to help let me just say thank you up front, i really appreciate it! Ive been scratching my head trying to figure out cathode bias value calculations and failing miserably.

[GibsonGM]

Hi Shad, graphics are wicked small...at least on my end... 

[ShadSunsCrash]

Yeah they are, i made them as big as i could but in order to see the full size image youll have to click on it and it should then be big enough to make out. If its still not after opening them just let me know and i resize them again on my own then reupload them. Thanks for taking a look!

[bluebunny]

I think Mike was clicking on the thumbnails.  They're still somewhat on the small side, even when "full size".

[r080]

PDF link might help. Here is the the MOD 102 to 102+ conversion pdf:

https://www.modelectronics.com/sites/modelectronics.com/files/media_files/mod102_to_mod102_conversion_0.pdf

Schematic on page 5