Just want to note here that the EIRP maximum for FCC is 36 dBm. Therefore, when using a 17 dBi Yagi, the radio Tx Power should not exceed 19 dBm.
We have had several customers report that the 450i 900 MHz radios connect even when the PMP 100's struggle, and have proven that in our own outdoor testing. Feel free to watch the webinars here where I discuss this (I have charts and data and everything!)