Completed fabrication of ELT mount plate. Cleaned and deburred. Located, drilled, dimpled and flush riveted nutplates (10-32 screws) to mount plate. Drilled rivet mounting holes in stringers and S4 bulkhead, then riveted using AAPQ-42 rivets to stringers and AAPQ-41 rivets to S4. Mounted ELT mount tray to ELT mount plate w/ 10-32 stainless screws (used Blue threadlock). Mounted ELT with provided strap. Removed right top tailcone skin and located VHF #1 antenna mount doubler to check location and clearances. Measured length of RG400 cable required for VHF #1 antenna cable and ordered same.