Correction, real woven cloth (like your tartan) doesn't stretch like that, there are many knitted fabrics that would..  =)

I was kicking around the idea of doing a version with princess seam mapping... I didn't want it to be the only version 'cause texturers would likely complain.

I've been sewing for 20 years, did bridal alterations for a good while profesionally, and have awards for medieval costuming...  don't have to tell me anything about real life fabric, construction, pattern drafting, etc..