About, "Does the EXT T/R Delay set the delay onset of RF to the relays to be sure you're not hot switching? Or, does the EXT T/R Delay set the amplifier's hang time?" The latter. RF drive to the amp is delayed at a fixed 15ms. The delay time setting in the menu is the amp's hang time only. 73, Roy K6XK P.S...it's all in the manual.