Thank you! The seam embroidery is based on real finds but I've also taken some liberties with it (like using two colours instead of just one), considering we'd be 90 years in the future and... ok that was an excuse, I just wanted to do it like that. 
The stitch type is based on Mammen wire embroidery finds. As for the collar, I just kind of took ideas from the wallpaper that showed the crew as they were before they ever signed up for the trip. Sigrun's tunic collar opens at the chest and seems like it could possibly-maybe have the otherwise trademark ribbon decorations nearly every military uniform we've seen so far has and imitated that with embroidery.
For patterns both the tunic and the shirt follow the same pattern you have in your link, except the shirt underneath also has a rectangular collar cover like the one shown here (scroll down a bit). Scroll a bit further down and you'll find the pattern I used for the trousers - I didn't have a ready pattern so I just calculated the right size for each piece for myself. It was a bit a lot of work but I think the end outcome looks pretty nice! Still, SSSS happens in Y90 so you don't have to be "viking-accurate" when you make the cosplay unless you want to, in which case high five fellow clothing history nerd!
Thank you for opening up the process! And that link is awesome - you're right, I just wanted to make it viking-accurate
Hello! But I'll be using my sewing machine and overlocker, since I just don't have that kind of dedication.
Shirt inconsistencies: I think the likeliest explanation is that the overtunic can easily be removed and that the shirt is the default everyone wears normally. Maybe I'm trying too hard to logic this, but the way I see it is that Lalli simply put it on between those two pages while the little steamboat takes some time to travel past the old city. Maybe he got cold? In any case I'd say you can go either way, only use the shirt or a shirt + tunic combo, both exist in canon as you pointed out. Same goes for the collar, since you have "options" in canon you can just go with the one that you like best. Tuuri and Lalli's shirts should be similar in my opinion, they're both in the military and the shirts are a part of the uniform so... same shirt, different sizes. Post photos when you're done by the way, I wanna seeeee~
That's a lot of trying
imo I don't think Lalli would in any way have the time to take a shirt off between pages 90 and 91, but that's beside the point. How do you think the collars work then? There wouldn't be much sense to have two embroidered blue collars with big ribbons sitting one on top of the other, but if I simplify the undershirt's collar, that kind of shirt isn't canon anymore... Ugh
Now I'm also questioning my fabric choices, I thought I'd do linen for both shirts, but wool might look better in the tunic (and be "more" accurate, according to your link). On the other hand, we'll be wearing those cosplays in summer. Hmm. But yeah, I'll def post photos as soon as there's anything to show.
