Installed the ELT antenna (2nd antenna of 4) aft of the comm antenna 2.5 feet. Was a straightforward installation even if I did have to spend 20 minutes on my knees up inside the fuselage! I'm really glad I thought to add the internal skin doublers before installing the rear top skin. Adding doublers from inside the fuselage (on my knees!) would not be fun.
ELT antenna (left) 2.5 feet behind the VHF comm antenna.
From inside: Antenna mounted through doubler with cable temporarily attached.