1 and 2 of this series.
Next up on my t-shirt block pattern transformation to a cardigan is to work on the pattern pieces for the back. I won't go into too much detail because there isn't much difference from the front.
Trace off the back and add the same length and width adjustments as the front. Extend the shoulder the same amount. Drop the armhole the same amount.
I also modified my sleeve for length and width. My previous blog post on how to reduce/eliminate sleeve cap ease* should give you an idea of how to adjust the sleeve cap. Walk the sleeve cap along both the front and back armhole of the bodices pieces. The armscye should be longer than the sleeve cap. Note the difference and enlarge the sleeve cap so that it matches the armscye. You can do this by slashing and spreading. Do not add any sleeve cap ease. This is a myth perpetuated by pattern drafting manuals and others. You don't need it.
*I've only recently discovered that some of the images from my older blog posts have disappeared into blogger's blackhole. I will try to fix some of them as I have time.