I just completed the installation of a GDL-82 in my 2001 RV-8 (I'm not the builder). The good news, I just completed the validation flight and have all green and got the Incentive Code to apply for the rebate. The bad news, I started all this on December 22nd.
The long span is all my fault and the result of a few things, 1) even though I thought I panned ahead to have everything on hand, I still needed to order a few things, 2) I planned to do it over the holidays so getting the things I forgot took longer than usual to get, and 3) I had no idea where I wanted to mount everything and spent a lot of time working out logistics.
This is simply intended to show what I did. It works, so it is a viable option, but not necessarily the best or only option.
The first consideration that took a lot of time to resolve was where to put the GPS antenna. I have a Garmin GNC 250XL so there is already a GPS antenna on the turtle deck. I considered putting the new one next to and farther aft of the one that is there, but to maintain the 9" minimum, 12" preferred distance between antennas that idea became untenable.
I then considered replacing the 250XL antenna with the GDL-82 antenna and just living without GPS on the 250 XL (I have an Aera 660 and an iPad running Fore Flight), but I didn't really like that idea. I also considered replacing the 250 XL antenna with the GDL antenna (they use the same hole pattern) and using it to provide GPS data for both units using a splitter. The problem there was more wires to run, another piece to mount and another $300. I ended up using the antenna shelf from the RV-12 (current part number F-01201R-1) on the firewall and mounting it there. When complete, it looked a lot like this:
The next issue was where to mount the box itself? I spent a lot of time on this one. Some of the areas that I considered but ultimately rejected are: under the front seat, on the rear baggage shelf, on a shelf behind the rear baggage bulkhead, and inside the forward baggage area.
What I finally settled on was on the rear (cabin side) of the aft bulkhead in the front baggage area which is behind the instrument panel. It looks like this:
This was reasonably easy to get to, was convenient to other wiring, didn't cost baggage space in the forward hold, and has it out of sight. The excess coax from the GPS antenna (6.5' minimum) is easily coiled up and secured out of the way.
Since the original transponder (GTX 320) had RG58 coax from the transponder to the antenna I had to replace that with RG400 as well. There was no problem getting 6.5' there, once routed it was actually more than a foot longer than that.
Once I figured out where to put everything the installation wasn't that hard (just a lot of crawling in and out of the airplane and under the panel).
I want to give a solid shout out to the folks at Stein Air, and particularly Christer Stenstrom, for answering all of my questions.
I also want to thank the previous owner, Carl, for his help in getting this installed.
More pictures can be found here: https://steverush.smugmug.com/GDL-82-Install/