After checking other builder websites, I decided that the best spot for the ELT would be next to the baggage area.
I fabricated a ""longeron"" piece to go between the 1st and 2nd cross-members in the aft fuselage. I notched the ends, then drilled holes to be used for riveting the shelf itself later on. The ELT is supposed to be oriented as close as possible to the direction of travel, so this longeron should be straight.
I then fabricated the back side of the shelf that will sit on top of the longerons. I'm not certain whether I want a ""box"" type area in front of the ELT for things like oil, or cupholders as several builders have done. I guess I could go with cupholders and just fill a spare round bottle with motor oil!! Anyway, I will eventually fabricate the front portion of the shelf once I decide on the configuration.