Can you give a little more detailed definition? (BT what to BT what, with fairings covering what sort of lengths, etc; maybe even a sketch?) PM me if you want.
I'd be happy to try to help, but I am not sure what you are looking for
I'm trying to attach the rocksim file for the 36d squared. I see a part listed as "Virtual Tube" in the design file. I suspect that is key to allowing parallel tubes. If that fails, look at the apogee technical reports or possibly a saturn 1b design file.