I am seaming a baby sweater made in K2P2 rib.
I’d understand how to seam the shoulder if they were all knit stitches; it’s the sewing of the purl stitches in the ribbing that I can’t figure out. I understand how to seam the vertical seams, but the shoulders (and probably also the sleeves by the time I get to them) are confusing me.
I even took out the bind off row to see if I could do a three needle bind off for the shoulders, but when I was done I could see the knit stitches in the seam on the purl part of the ribbing.
Then I tried a three needle bind off using knit and purl stitches, but that looked even weirder :??
I was going to have trouble anyways on the other shoulder, because of the way the instructions read (bind off 17, pattern 22, bind off 17; put the remaining 22 sts. between the two sets of bind offs on a needle holder that were later picked up for a shawl collar), there is no tail there to help me undo the bind off on that side- it went into the collar.
So, can someone help me figure out:
A. what kind of seam I should use for the shoulder and
B. where I went wrong with the three needle bind off
(I thought I read somewhere that to do it properly both sets of stitches to be bound off need to be heading in the same direction. In other words, on the left front (as it is worn) the row done before the bind off would be a WS row, and the row done before the bind off on the back would also be a WS row, and on the right front (as it is worn), the last row before the bind off should be a RS row, and on the back it would also be a RS row so that both shoulder seams would be bound off towards the neck).
Sorry this post is so long…I’m so confused right now I don’t even know what I don’t know…help! 

