The ELT is a fairly straight forward installation. The bracket that is at the rear needs to be installed before the fuel tank goes in, but the bracket isn’t delivered until you buy the avionics package. There are two holes in that bracket (not visible in the photo) and no clear instruction as to which one is needed. you can guess which ones I used first. I ended up installing this about 1 cm too far aft, and needed to drill out the unusual rivets you see in the bracket. Luckily, I had the spares on hand.