I'm certainly no expert, but a few things come to mind...
If you want the armhole to dip lower, you could do a few more yoke rounds before separating the body and sleeves. Alternately, you could divide at the same place but cast on more stitches under the arm to widen the opening. Note that either of these fixes will increase the body width in addition to the sleeve width. If both your body and sleeves turn out to be too wide this way, you may want to adjust your rate of increasing.
If the problem is caused by the body being too wide in relation to the sleeves (body loose but armholes tight), you could adjust the body:sleeve ratio moving some body stitches to the sleeves (i.e., keep the overall number of cast on stitches the same, but move where you do the raglan increases). This will make the arms larger while making the body smaller.
I think I remember the article on short rowing that you're referring to, but don't have it bookmarked. Honestly, I think the easiest thing would be to cast on a few more stitches under the arms. If the body seems too wide after you do this, you can put in some decreases to make it narrower. (I read this in a book so it must be okay!