Lest anyone think that little paper pieces are as simple as pulling out scissors and snipping away...
I did a lot of trial and error here. Here are some clear misses:
So, I had this thought while at work. Build a 1" square base support. On top, I can put these little lip pieces in the corners or along the middle. That would help hold the 1" catwalk in place. It seemed brilliant in theory, but a couple of things failed. First, the piece is wobbly. It doesn't anchor to anything. Second, the posts get in the way, so I can't position these where I need them. Finally, it certainly doesn't fit in with any TLX style pieces. Oh well.
After that attempt, I went really basic:
Well, this certainly is kinda TLX-ish. It slots into the posts, and is really flat and easy to build. Unfortunately, without any width, it doesn't do much to support the ends of the catwalk pieces. NEXT!
I've got a metric tonne of walls sitting on my desk right now, and many of them have the anti-warp triangular edge on them. Wait a minute... triangular edge! That's what I'll do!
Sadly in my rush some basic math eluded me. I was going to make a box, so I measured out each edge 1/4". But then I decided triangles are good enough for WWG, they should be good enough for me (and they're sturdier!). So I lobbed off one flap, and glued it into a triangle. As you can see, this causes the top to not be flat. The darn hypotenuse needs to be longer than the sides.
I like this one. It again slots right into the wall, but it's got ledges on both sides for ample support of either the ends or the middle of a catwalk piece. It's still not perfect - I'm going to try to make it easier to build a more reliably flat top. I might also try making some sort of... I don't know... something that might hold the catwalk piece in place more snug. Still trying...