BUT, before we do, here's a little disclaimer. I have seen MANY people in the Halla Stardust Tank. I would say the majority of them had plenty of coverage for their bra straps. So, you may not need this adjustment, at all. I have wide shoulders and my bra straps tend to sit towards the end of those shoulders. That is unique to MY body. So, you may want to try the pattern, AS IS, before you bother making this adjustment. Further, you can use this same adjustment on a pattern that has a too wide neckline to bring the neckline IN.

While I am using the Halla Stardust Tank for today's post, this method will work on ANY tank pattern (knit or woven) to extend out the shoulder seams.

Ready?

You will need:
-Tank pattern of your choice
-Paper
-Tape
-French curve
-Ruler
-Pen

First, trace out a copy of your tank pattern, including at least the armscye, neckline and shoulder.

Second, extend out the shoulder seam following the angle of the shoulder seam. You won't need very much extra here, but I usually draw out at least an inch. And often, I go a little crazy. ;)

Third, if you already have a muslin of your pattern of choice, you can measure how far over you need to extend the shoulder. In my case, I knew that my bra strap was 1/2" beyond the armscye band. For a little extra coverage I knew I wanted 5/8" more added to the shoulder. You can extend the seam as far as you want (including to the point it becomes a cap sleeve). Mark your shoulder seam the amount over you intend to add.

Fourth, using your french curve, redraw the armscye, connecting the point at which the pattern starts to curve up to the mark you made on the shoulder seam. You can eyeball that point on the pattern. Or if you have a wearable version, you can mark where on the armpit you feel that you have sufficient coverage and match the curve from there up to the shoulder.

Fifth, make the same adjustments to the back pattern piece. (not shown, but the same method as above.

Sixth, chances are, your adjustments shouldn't make too much difference for the truing of this pattern, but, if you're obsessed with having a trued seam, now is the time to check your pattern pieces. I skipped this step (out of laziness).

Finished pattern piece

Now that your pattern pieces are done, you will need to measure out your bands for the neckline and armscyes. I have been opting not to measure and just using the tension of the bands to ease them into place. This is an art and something I am working on perfecting. Obviously not for the faint of heart. If you opt to measure instead, depending on your fabric, you will want between 80 - 85% of the opening for your bands.