Modifying from V-neck to jewel neckline

I’m knitting a sweater for my husband (“Geoffroy” in Norah Gaughan’s “Men” issue from Berroco). The only problem is that he doesn’t care for the V-neck shape, and so I told him I’d make it as a jewel neckline (regular T-shirt style neckline). While I’m tempted to just have a go at it, I’d appreciate any general tips for this type of modification.

I’ve currently got 100 sts on size 5 needles after binding off for the armholes (the pattern is the same all the way across). Is there a general rule for a T-shirt style neckline? They always seem to call for a big bindoff, and then decreasing 1-3 sts each side on each row for some number of rows after. Is there a formula for the % of the total sts I should bind off? Or how many I should decrease and for how many rows thereafter? I’m generally doing worsted weight sweaters, so I’m hesitant to try and convert that over to a smaller needle.

Thanks much for the help!

Keep following the armhole edge shaping, that won’t change. Knit all the way across the front until about 2" below where the shoulders will end. That’s called a crew neck and very common. If you can find a regular sweater pattern with a similar number of sts you can follow those instructions for the neckline shaping. Or at least with a little math, that should give you a percentange to follow.