Caligae Construction

[Neuraleanus]

Does anyone know of the actual archaeological basis for believing that Legionary caligae were constructed by stitching across the back of the heel and up the back of the ankle/ lower leg section? It strikes me as a design with an inherent weakness at a point where there's a great deal of stress on the sandal. Are there actually artifacts that show these seams? The few images I've found don't show this area sufficiently to really tell.

I stitched the backs of my new caligae using a reinforced vertical double running stitch because that was the way it was shown in the book, "Stepping through Time". There are also illustrations of caligae having this kind of back seam construction in Faugeras's book, "Weapons of the romans". This construction appears to be quite strong. I also used 5-7oz leather. Another point is the use "bumps" at the locations where straps join (see the pattern that I posted). I suspect that these bumps are more than just decorative, but serve to reinfoce the strap joins.