You have any issues with the struts breaking? In this design the cargo bay is not nearly as large as your original, but underneath that floor are enough fuel to provide 2800m/s or so of delta v. Even still, has more than enough room for 1.5m parts and with my redesigned layout allows for larger payloads(hinges at the ends v middle of door). As is part count is 189, but still needs more work/parts.