I use 250ml of chemistry (+ or -) in Cibachrome 8x10 drums for single sheets of 8x10 film. (I don't use much more than this because the fluid will start seeping from the drain holes in the bottom of the drum.) I use a motor base that reverses, but before that I would pick the drum up and turn it around once per minute when using a base that rotated in one direction only. My starting point for development times due to constant agitation is usually 15% less than recommended for small tanks.

Just be sure to fix the negative in a tray after you've fixed it in the drum to ensure that all of the anti-halation dyes wash out before final rinse. There is not much fluid exchange along the back side of the negative that is plastered to the wall of the drum during processing.

Jonathan