The Dhvajastambha, as we call it, is installed based on the Agama pertaining to that specific temple. The details of the size, height, quality of the wood to be used and so on are specified in the Agama concerned. PAncarAtra and VaikhAnasa are the two main Agamas followed by the Vaishnavite temples. There are many branches of PancharAtra Agama. The North Indian Temples are not based on PAncarAtra and VaikhAnasa Agamas. Hence depending upon the Agama / Scripture followed by the Temple, there are variations.