Double output battery charger

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Hi, I have to design a new battery charger with two outputs 27.5V 0.5Amps. In the attached scheme resulting from PI Expert 9, the feedback voltage is connected to only one section, while I need control on both sections because, having to charge the batteries, I might have a section that requires more load and the other less. With the proposed circuit by PI Expert, it seems to me that if  on the 'uncontrolled' section there is little current consumption, while in the controlled section there is a greater absorption, the voltage on the 'uncontrolled' section goes up improperly. I wonder if it is possible and recommended to create another equal feedback for the uncontrolled section and put the optocoupler output in series with the first optocoupler. There is a better alternative ? Can you give me a little help ? Thank you very much in advance, Emanuele Castagnini - SMS Sistemi e Microsistemi - Tech. Dept.