Determination of similar uses. In order to permit uses of a similar character to those prescribed in § 306-7C as permitted in the R-1, R-2, R-A, C-C and H-D Districts, the Town Planning Board, on its own initiative or upon written request, shall determine whether a use not specifically listed as a permitted use should be authorized. In making this determination, the Planning Board shall consider whether the proposed use is substantially different in size, operations, impacts and other characteristics from uses permitted in the same district. If the proposed use is found to be similar to uses specifically listed and appropriate in the district, the Planning Board shall authorize the use as a permitted use in the district.