Follow up with final product...
After several failures with thread, I switched over to a stamp. I designed a small stamp with MeshMixer (free) and printed it on a Formslab desktop SLA printer (not free). The first attempt I stamped it then added a white wash with some leather paint - I didn't like the results on this one because 1) the leather was too thin so the impression wasn't deep enough, 2) too much smudging and white ended up in the deeper stamped portions. The second attempt I used a thicker piece of leather (3/4 oz) and left it natural. My friend (customer) preferred this look after seeing both. Here is the final product on the cowboy hat. Not perfect but all things considered I'm happy with the result. I priced out a custom stamp from a handful of companies for $85-105. I spent a total time of 2 hours (designing, printing, washing, and curing) and less than $1 on the printed stamp, superglue, and a scrap piece of wood from my shop. If I print another I'll do a set of 3 or 5 for longer sections and less chances of seeing each individual stamp lines. Let me know what ya'll think.