I beg to differ. If you look on the bottom of a Paterson tank it states 295ml for one 35mm film. 500ml is for 120 and Matt mentions using a litre?
For me, it is a matter of consistent, repeatable results. Yes, I understand that 500 ml of fluid requires a 120 tank, but using D-76 diluted, requires 500 ml of the diluted solution, otherwise I have sometimes had underdeveloped negatives. I quit playing that game a long time ago. I got tired of thin negatives, as the OP has described.
"She's always out making pictures, She's always out making scenes.
She's always out the window, When it comes to making Dreams.
It's all mixed up, It's all mixed up, It's all mixed up."