Did this a couple years ago with a good group of friends. Not particularly hardcore compared with some of what's in here, but novel.
Started in Paso Picacho Campground. Up Cuyamaca to the summit, down the west side and then west on an improvised/google earthed route through sometimes, we later found out, private or reservation land. Some truck trail. Some bush whacking.
Overnight in the four corners area of Ramona where we had cached a tent and some canned foods. Then back at it in the morning.
Around the east side of El Cajon Mountain and down through to Lakeside. Then through Mission Gorge and subsequently a flat long slog in the dark to Fiesta Island in Mission Bay.
Missed a turn and meant to finish at Torrey Pines State Beach, but it didn't pan out that way, so we called a cab at the Bay.
Finished at 1:30am. Makes it approximately 1d18hrs.
GPS measured somewhere around 63 miles.
5 started. 3 finished. 2 dropped out from wicked blisters.
Unlikely it's been repeated prior or subsequently, but I'd love to hear if it has.