I think 500ml should be more than enough developer. I use that amount all the time to develop one 120 roll of film.
Phenidone: .75g
Sodium Sulfite (anhydrous) 13g.
I use a 50gr Phenidone dilution on 1000ml of Glycol. Use 15ml for 500ml of developer.
LIke Craig said, POTA is a good developer for high contras film. Also good when you shoot film on very contrasty environment. Bring out a lot of tonal range. I love what I can get with it using Aviphot film.
It lower film speed (about one step) and grain may not be the best for certain films so not your everyday cup of tea (of coffee). I use it when speed is not essential (like portrait/lanscape). Got hold of a big roll of Aviphot to cut for 4x5 and intend to use it with POTA @100.
Mamiya C330 80mm f/2.8 Aviphot 40 @40 using POTA developer (14min at 75F).