Setbacks. Appropriate minimum setbacks in an open space development depend upon the lot sizes, the type of road frontage (state, county, Town, or private) and the character of the subdivision (hamlet, suburban, or rural). Accordingly, the applicant shall propose, and the Planning Board shall approve, setback (or build-to line) requirements at the time of plat approval. These setback requirements shall be shown in a chart on the plat. New structures in an open space development shall be set back a minimum of 300 feet from existing dwellings on lots that are not part of the open space development, unless the Planning Board finds that site conditions, lot configurations, or the conservation analysis make this requirement infeasible or inconsistent with the purposes of open space development.