Hi Bob,
I did a repair like that on a 1994 Snowbird.
While it is not the actual tie down location, but the corner, many of the methods could be the same.
First, I had jack supports that wrapped both sides of the corner, and had a tab underneath as well for vertical support. These were aftermarket fabricated, and of course were the first thing off the corner. As I pulled the various screws and lag bolts out, I realized that there was really nothing solid behind them. Layer upon layer was then peeled back, until I got into the actual frame, and I realized the 1.25 by 1.25 corner post was completely rotten from the bed extension to the bottom. I removed all that I could, and treated what was left with Git Rot to preserve and stabilize the rest.
Then I fashioned a new corner piece to fit what I had removed, and dry fit it perfectly. I then fashioned other pieces some solid, and some plywood that would extend into the various directions of the corner and upright frame and adhere to the remaining wood, and dry fit each piece with great care and precision. This essentially provided a much more solid and thick corner.
Once I was happy with the dry fit, I coated each piece with the Git Rot solution to preserve the pieces, and let them dry. From there I began the assembly and used their Git Rot Epoxy and glued and clamped each piece in place, one at a time and let the epoxy dry between pieces.
Once the corner was totally solid, I drilled it out for bolts to hold the corner bracket on, and put it all back together again, finishing up with the jack bracket glued on with Sikaflex and bolts.
Do a search for Git Rot, and you will see the products and their uses. It worked perfectly.
Mike
2012 Winnebago Impulse Silver 26QP
2005 16.6 Double Eagle
2018 Jeep Wrangler JK
previously Snowbird Campers,
Triple E Motorhome and Fifth Wheel