"Or is it necessary to perform a hardware mod to get it to do so? If so, is there someone who has done the mod (successfully) who can provide documentation on what he did that worked?" There is a surface mount diode (D523) that needs to be removed to allow TX below 440 Mhz. Not the best documentation, but I followed this to modify mine:  http://www.qsl.net/kf4tuz/icomhacks.html By the way, if you perform the RX modification on that page (just pushing some buttons, no soldering or even screwdrivers involved) and you are able to access the 800 Mhz band, then you have one of the units that should work full duplex on SO-50 well. If not, then you will likely find it's only semi duplex on SO-50, but fine on the U/v birds.

73 & GL, Kevin N4UFO