Monthly maintenance for co operative housing society in pune, maharashtra

Hi, builder is going to handover society to the members of housing society. We have 28 flats and 14 more are going to be added in future. So currently we are having dispute about how the monthly maintenance should be calculated. Small flat owners say by per squre feet area of each flat and big flat owners say by per flat basis. We put argument that as we are having all the amenities equally shared with all flat owners, the running maintenance costs like lift, electricity bill for society's common area, security guard, cleaning of the society common areas, garden, cctv camera should be equally contributed by each flat owner irrespective of the area of flat.