Seaming a sleeve with decreases along the edge

I am hoping someone can recommend a seaming method for the sleeves to body join of the sweater I am currently finishing. The issue I have encountered is the pattern wanted decreases along at the edge of the sleeves. I, foolishly, went along with that and am now left in a bit of pickle. My moderate amount of sweater seaming has been done using patterns that wisely suggested decreasing two rows back from the edge. Is my usual mattress stitch the way to go, or is there a stitch that works better in this situation? Thank you for the advice!

I like the back stitch for some seams. It’s shown here across rows but works well on the side too.

For me, it makes it easier to match up stripe patterns in case that applies.


When I did this I still used mattress stitch but just ignored the very edge where the decreases make it a bit messy. I think the result was a slightly bulkier seam on the inside but the outside was still lovely and neat as expected.
I thought I’d mention just incase you still wanted to go ahead with mattress stitch.

Maybe now is the time for me to learn back stitch.