Baseline system selection

Hello everyone, We are working with a building that has a complicated geometry, and the selection of the baseline system is not that evident. We are able to identify 5 main floors, but it includes an additional small conditioned area next to the building located at a lower level than the first floor. The total conditioned area is 146,000 sf. We would select a system 6 based on 5 floors or less and less than 150,000 sf, would you guys do the same? The reviewers might consider that the building has 6 floors, which would make the baseline fall under the system 8 category... Thank you for your comments