I've never tried it, but I'm thinking if you ask them for a custom ratio in the comment/special instruction section of the order, they would do it for you. That is as long as you're not trying to split hairs - "I'd like 72.25....%/ 27.75,,,% with 3 and 5/16 extra shots"
Keep it nice round figures, 10, 20, 30, 40, ... so on.
James and his crew are on the ball. This vender was one of the fastest turn arounds I've experienced and the
juice is pretty darn good too. Yum, banana nut bread. Butter Scotch and Peanutbutter cup are ok too.