So I had an idea. I work in 199 g/m^2 cardstock. this made the overlapped tabs for squaring up the stairs very thick. Maybe I wasn't getting the proper allowances due to too much thickness. So a I printed a new set on 28 pound bond. ( can't find the tag with the g/m^2) Print your own models can be very forgiving that way! Unfortunately the results were still poor.
Next I tried one where I didn't use the tabs to square each step one by one. I even cut them off. I folded the stairs and attached them to the balusters by simply butting the paper up to the flat. Still no joy. Maybe it is me.
As technique goes, the diagrammed instructions to fold over and square each successive step using the printed end tabs seems wrong to me now. Each step will be just a a bit off square. The face of the bottom step is supposed to wrap around the ascending balusters to form a pediment-like block on the outside of the staircase. (This interlocking of bits seems to be a feature of this design.) Here, it makes the fit of the base stair very fussy.
I'm also not sure that the actual dimensions are right. To jump ahead a bit after I got the base of the temple to my satisfaction I dry fitted some of the best staircases to it and they don't fit well. Notice how the cut out doesn't fit the lip of the temple, and partially as a result, the entire piece juts too high above the base. This will fix a bit if forced down as glued but not enough from my attempts without glue.
So any ideas? At this point I'm thinking I'll cut the pieces apart and nearly scratch build the darn things. Its seems its either that or fold a few dozen until I get good enough. (argh, I've all ready made seven of these things!)