I think I will join in on this one also.  I just moved my sewing room, and the amount of fabric I had to use, plus all that I gave away, was mind boggling.  I am also teaching my granddaughter to sew and I know she has been eyeing quite a few pieces of my stash, so I will get double sewn?

I do know how to do it, just not sure if I can explain it right. 

Turn your sleeve wrong side out.  You will be topstitching the seam with the seam laying on your machine bed, positioned just as if you are sewing the original seam.  You will be sewing inside the sleeve from the wider armhole to the narrower cuff, keeping the top of the sleeve free.  You will have to "scrunch" the fabric as you get closer to the cuff, bit as long as you are stitch on the single layer you will be fine.

Does this make sense?