Do you mean 1:4 from the original concentrate? If so, why not just use 1:7 dilution and do two separate batches of five and four. You'll end up using about the same amount of developer, and the smaller batches will be a lot less awkward to handle during the processing. What kind of film is involved? I routinely use 1:7 for T-100 and T-400; glad to supply my typical times if you want.