There a quite a lot of tutorials with this joining method, but not for ribbing and now I have used it I am really surprised that it is not put out there more. I’ve done my shoulder seams now and really happy with the result. My kni55jng was with 3.5mm needles and I tried 3.5mm crochet hook which I would say worked fine but I wanted to see what happened with smaller (tighter seam) so tried 3mm and 2.5mm and I kept the 2.5mm seam. It is hard to explain but it is very sturdy which is what I wanted for the shoulder but it is also stretchy and soft.
Just started the first sleeve. When I have the sleeves ready I’m going to try this slip stitch seam on a set in sleeve seam.