Except for consolidation of revenue allocation areas, a revenue allocation area may only be amended to extend its boundaries as set forth herein. An amendment to an urban renewal plan that does not seek to increase the geographic area of the plan, or does not seek to extend the years of the plan beyond the maximum term allowed under chapter 29, title 50, Idaho Code, is not a prohibited amendment, but may be subject to the limitations set forth in section 50-2903A, Idaho Code. No plan amendment shall be interpreted to or shall cause an extension of the limitations established for the existing revenue allocation area as set forth in section 50-2904, Idaho Code. Subject to the limitations in this section and section 50-2903A, Idaho Code, an urban renewal plan that includes a revenue allocation area may be extended only one (1) time to extend the boundary of the revenue allocation so long as the total area to be added is not greater than ten percent (10%) of the existing revenue allocation area and the area to be added is contiguous to the existing revenue allocation area but such contiguity cannot be established solely by a shoestring or strip of land which comprises a railroad or public right-of-way.