Here's my answer in a roundabout way...(posted 8696 days ago)I frequently use D-76 1:3, often with 35mm HP5+, using 300ml per roll. I also use it with 120, 4x5 and 8x10.
35mm x36 exp is about 80 sq in, same as a 120 roll, same as four 4x5 sheets. A 120 roll needs twice the amount of developer, and it's very easy to use more for sheet film, so 35mm represents the worst-case scenario.
The amount of D-76 stock is only 75ml.
In comparing HP5+ in D-76 1:1 and 1:3, given the extended development time needed for the higher dilution, I get identical EI, CI and curve shape. I get similar results for Delta 100.
My conclusion is that 75ml D-76 stock has sufficient capacity for 80 sq in of film. I haven't tested any higher dilutions.
A few tidbits...
TX 120 is a _different emulsion_ than TXP, and the 4x5 film is TXP only. Development specs for TX may not be the same as for TXP.
A reasonable guess for doubling the dilution (stock to 1:1, 1:1 to 1:3 etc) is to give 1.4X the initial development time. _This will probably need adjusting_.
D-76 diluted 1:1 has only half the sodium sulfite concentration as the stock, which may allow faster oxidation than in the stock concentration. That's the only reason I can think of offhand that you probably shouldn't mix and store diluted D-76.