Lowell, I doubled the fudge factor and Finagle's constant (2FF+2Fk) and mounted the ELT with 10-32 hardware. Yeah, 6-32 is a bit small in my book. [rolling eyes in unison with rocket scientist] My tray had #8 size holes.
What the heck, if I hit hard enough to rip the thing loose it probably won't be survivable, anyway.

The extra coax is part of the certification package for the TSO. I must use the factory length coax and the factory antenna for the TSO to be valid. The manufacturer says to simply coil up the excess coax. There's a lot more in the plane with the antenna in the v-stab. The other wire to the ELT is the remote activation to the cockpit wiring. (Also required if not in reach from the pilot seat.).

John