I’ve done this. Treatment of the inside edge of the TPU important if there is no lining covering it. Typically would have a lining material covering that edge to avoid a sharp edge. (BTW, these were out before the Adi posted above).
Part I believe was a nominal thickness of 3.0mm with the thin part under the leather 1.2mm. I don’t think we had a stitch groove, but rather just the thinner material to stitch through and the difference of thickness to help align the part.
See below-
R
