Yep, I homebrewed my 4) 813's in grounded grid amp.
FOUR 813's??? Wow that's impressive.
Since we're being off-topic here... years ago a friend of mine and I built a linear amplifier with a 3-1000-Z triode in grounded grid.
My buddy was adjusting the bias pot in the rear with the transmitter keyed and loaded up to full power. He reached over the top of the amp with his right arm and about a 2 inch long wicked blue with yellow fringes arc jumped from the plate connector to his arm.
It made a loud hissing sound and crawled up his arm like a "Jacob's ladder". In the probably 1/4 second reaction time it took him to yank his arm away and yell, that arc grew to 3 inches long and slashed a 6 inch long charred (no blood) gash in his arm.
The smoke and smell of burning skin was horrible.
That wound seeped and oozed for a good month. It would scab, then break open, then scab again, then break open.
At first it only looked like a thin black line, but it turned out to be completely destroyed tissue 1/2 inch wide and a good 3/8 inch deep.