I don't use D76 but I one shot HC110 at Dil B (1:31) for a dual reel tank (2-36 exp. 135-roll film rolls). I have used four rolls per one mixture (500mL) with good results.
HC110 at Dil B is good for the equivalent of 10 8x10 sheets of film per gallon (3.8L). That's 100 square inches per pint (500mL). A 36 exp roll of 135 is about 55 square inches. That would indicate that you could safely soup two rolls per 500mL mix.
D76 straight will do 10 rolls of 36 exp 135 roll film per gallon. That is 1.25 rolls per 500mL straight solution. You should be able to get by with two rolls. The life for D76 1:1 is eight rolls. One per 500mL mixture.