As you can see, I kept the bust dart because it was the right proportion. I also really like using darts with knit because the detail elevates the t-shirt to a higher level. At the existing lengthen/shorten line, I took out about 1.5". With the silky shirt, the extra length makes it more dressy but with the fine knit, I think it will just hang down and look messy. Finally, I redrew the entire hem. I was wearing a shirt with a hemline that I really like so I took it off, set it on top of my pattern, and traced it. I'm sure the new neighbors liked that one.
The back is where I made the most changes. I started with the hem and length changes from the pattern front (you can't forget to do both sides!). Then I removed the shoulder dart and eased the fabric to the middle. Next I just eyed up how big I wanted that top panel to be (see my inspiration photo here) and drew a line perpendicular to the grain line since the middle back seam has a curve to it. I cut on the line and then added "darts" for the gathers. You can see in the photo where I added the blue to show you that. I wanted to keep the waist slim so I used that as my pivot point. I just started at the top edge and cut a straight line with scissors to the waist. Then I split the paper apart until it started to buckle just slightly then taped some paper from the recycling bin to the back of the pattern. (I should have used colored paper -- that's how I was taught. That way if I were to make changes to this pattern and use it again, I'd know what was original and what was added.)
The back is where I made the most changes. I started with the hem and length changes from the pattern front (you can't forget to do both sides!). Then I removed the shoulder dart and eased the fabric to the middle. Next I just eyed up how big I wanted that top panel to be (see my inspiration photo here) and drew a line perpendicular to the grain line since the middle back seam has a curve to it. I cut on the line and then added "darts" for the gathers. You can see in the photo where I added the blue to show you that. I wanted to keep the waist slim so I used that as my pivot point. I just started at the top edge and cut a straight line with scissors to the waist. Then I split the paper apart until it started to buckle just slightly then taped some paper from the recycling bin to the back of the pattern. (I should have used colored paper -- that's how I was taught. That way if I were to make changes to this pattern and use it again, I'd know what was original and what was added.)
I did this until I felt that I had enough in there. Then I drew a line with a ruler to clean up the top edge and added seam allowances to both pieces. I added a little more to the top of the sleeve pattern (not pictured) to give a little more gather to that using the same slash method. Since the existing belt pattern wasn't long enough, I added some length to that and also made it just a little wider. I'm not sure if the belt will look right with this but I'll make it and try it out. I made some adjustments to the collar to make it somewhere between a band collar and a Peter Pan. I have no idea how that is going to work. I did like the way the Simplicity shirt looked without a collar so that's my backup plan.
The waist of the original pattern is almost fitted. You can see how the pattern has a really nice curve there. I'm not sure at all how my gather adjustments are going to look with that. If you want to try my improv method of pattern alteration: Make sure you use the right marks on the armholes and sleeve pattern. One means the front and one means that back. If you mix them up, the sleeves will not fit. I often chop my little triangles right off; if you have a good pattern and you cut straight, your stuff should line up. I'm lazy but I do not cut corners (ha ha) on sleeves.