Burda sleeve alteration: help please!

And this is why I didn’t make that separates resolution official.  After cutting out the fabric for the tops I figured I had time for a quick dress muslin.  This Burda dress has been on my to-do list for almost a year now.  I first saw Elaine’s version and set about looking for the perfect piece of gray wool.  Then I saw this oatmeal heather version from the original magazine issue and I thought that’s what I wanted.  But I think I’ve finally found the perfect fabric: this beautiful worsted wool from fabric.com.  The threads are gray and brown and sienna and the overall look is a sort of taupe-ish blueberry gray. The weight is perfect: smooth and lightweight but with some stiffness that I think will work well with the pleats.  And it’s a small scale plaid.  Could it be any more rooish?  Oh yes, and I ordered 2 1/2 yards but they wrote me and said they had only 2 yard cuts left.  I said that was fine and they sent me two 2 yard cuts (!).  So I should have enough for a jacket too if I’m careful (or a skirt if I’m not).

For some reason I had it in my head that I was going to make this dress without a muslin.  I have no idea why.  This time I just muslined the bodice.  After comparing the pattern to my sloper I lowered the bust point by 1/2″ and straightened the shoulders by adding about 1″4 inch to their sides.  I widened the sleeve pattern to match what I had added to the shoulders.  I didn’t think the back would fit that well but I made it up as-is to see how it fit.

What do you think?  I think the front fits okay although I can’t tell if I should add a bit more fabric to the bottom of the bodice (what I’m showing includes seam allowance).  Maybe I need to go ahead a muslin the skirt as well after all.  The shape of the back looks okay but it gapes quite a lot at the bottom (see arrow in the side pic below).  And this is after I took it in about 1/2″ at the bottom.  Do you think the gape is okay or should I take it in more?

The other problem is the sleeve.  It felt a little tight across the shoulders and looking at the muslin I can see some pulling on the sleeve (see other arrow).  It’s just tight enough that I’d probably go ahead and make it and then find myself never wearing it because it didn’t fit right.  So I think I’d better fix this problem now.  So my question is: how do I add space to the sleeve without changing how it fits into the armscye?  If anyone knows the “right” way to do this I’d be very grateful.  Otherwise I will just have to continue my experimental sewist ways, and it will probably be four muslins before this thing actually gets made.  Also do you think it is necessary to muslin the skirt?  I figured since it is A-line and has all those pleats there will be room to adjust but maybe I should just go ahead and do it.  Just that I’m getting towards the end of this bolt of muslin and feeling a bit sheepish about it.  (Although David did point out that muslin scraps make good painting rags.  I don’t know why I didn’t think of this before.)