A couple of the patterns I've worked on have had a back opening to a dress or top, but on the pattern or instructions, the opening only goes down to the seam line where the yoke joins the gathered skirt part. On both of these, I have wanted to extend the opening down beyond that seam line to make getting the garment on and off easier. The challenge is not that the opening is insufficient to allow the head through, but that the seam line itself causes a constriction when it comes to getting shoulders and elbows through. Just a little further opening down below the seam is a help.
1. Edge to edge opening
One such pattern, the free PDF for the Izzy top, is one I love, but I've previously had to resort to making a larger size to deal with the shoulders and elbows issue! It is designed as an edge to edge opening in the back yoke, attaching to a gathered skirt. The back skirt in the Izzy top is made all of one piece, cut on the fold.
Here's how I extended the opening.
I took the pattern piece for the skirt, which says ' cut one on the fold'. (But you could do the same thing if you had a pattern with a centre back seam in the skirt.) I added about 1 1/4" to the width, and treated this new line as a cutting line.
I then treated the original fold line as a seam line, but I only seamed from the bottom to a little short of the top - say 2" to 3" short. (Obviously right sides together.) It's important here to reinforce the top of this seam. Having sewed up the seam, I trimmed away the lower part of the seam allowance. You don't have to do this, you could just leave it with a very wide seam allowance, but I think it looks neater to trim it. Note that I only started trimming well below the opening I'd left in the seam, that way you won't have raw edges on show. You could cut it straight across, but I thought it looks better angled as I've shown it.
The next step was to open the back out, and press the seam allowances away from the seam. Then I finished the edges. If you have a serger, you could serge the edges. I don't, so I chose to do a fairly short (but wide) zigzag across the edges, Alternatively you could use pinking shears or turn in a tiny single hem. But the zig zagging worked for me,
And voila - a top that opens just that bit further, and should be easier to get on and off.
2. Overlap opening
I had had a similar problem with a pretty pattern from Cottage Mama when I made Christmas party dresses for my grand-daughters eighteen months ago. This pattern also has a back opening for the top part, attaching to a gathered skirt. There was the same issue, though, in that that the waist measurement in itself has little 'give' to go over broader shoulders (or hips / butt encased in a nappy, if you pull up instead of down).However, it is different from the Izzy top in a couple of ways. Firstly the yoke is more of a full bodice that comes down to the waistline. Secondly, the back opening has an overlap, in other words the centre back is not on the edges of the opening, but about half an inch in from each side, with a one inch overlap.
This overlap opening presents a different challenge if you want to make the opening a bit deeper, as I did. If your skirt seam is in the centre of the back, it's not going to line up with the overlapped edge of the bodice part. If you line it up with the overlapped bodice edge, it won't be in the centre. I spent several nights awake trying to figure this out.
If your opening extended all the way down the skirt, the not centredness might not matter. Sew Mama Sew has made that assumption in this post, but the opening is in the front. I think it might be a bit weird with an opening all the way down the back of a skirt. With the Cottage Mama dresses for Christmas, I played around with adding extra one side of the skirt pattern, then the other side, then a bit more the first side - and I was never very happy with the results. I ended up having to fudge it a bit. You can just about see that the opening goes down below the waistline, but however hard I fiddled with it, I couldn't find a way to get the centre back line of the skirt to be anything other than off-centre!
Maybe I was being extra fussy - I don't suppose the toddler who wore this noticed at all! Eventually I concluded that (for someone of my skills at sewing, or lack of them) I would just have to assume that the "centre" back seam for the skirt would by slightly off centre. After all, the difference is pretty small. If anyone knows how to deal with this, I would be very interested to hear from them - a search on the internet hasn't given me any more ideas.
However, since I first wrote this post, I read more about how to add a continuous bound placket - this means you don't need a seam all the way down the dress so the fact that the opening is slightly off centre isn't noticeable. I'll use this approach in future, I think - and if I do, I'll write about it! In the meantime, I'll continue to extend openings below a fixed yoke or waistline seam, unless that seam is elasticated.