What would be the best method to convert a shirt like this?

Oh you could probably do it without sewing at all. Or very minimal. There is this stuff used to reinforce zippers its fabric strips wrapped around a piece of cardboard and the strips are folded so it opens to various widths. All sorts of different colors you could use a simple or even decorative stitch to hold in place after pinning it they way you desire for the trim.

Other options include fabric markers. Seems somewhat cheesy. But there are some good fabric paints just tape off the area and put something cardboard inbetween front and back you can test this on some old clothing.

Another option is bleaching the area, this technique is widely used with tiedyers so visit a website and practice it before you give it a shot on the real thing.

As to the v in the turtleneck it’s difficulty might lay in fabric type and construction but you could do something a simple as cut not below the start of the tunic and gets some fabric glue or fusable material. If the neck gets floppy and is a flod type construction you may be able to insert cardboard collars, use starch or stiffener, which would be less permanent or reinforce the back with a stiffer fusing see quilting notions or tshirt embroadiary packets…

To shorten the bottom will be easier you can measure twice cut, fabric mats and rollers are best for this but you can make do. Measure pin and seam.

all materials can be found in a joanns or michaels or sometimes even walmart.

If it already fits you the way you want it to, it’s easy and only requires a bit of hand stitching and patience.

Buy the contrasting color you want “seam binding tape” wherever sewing supplies are sold. It’s a pre-pressed strip usually sold by 3 yard spools.

First, cut directly down the midline to where you want the neckline to be. Then, leaving a few inches at the back of the neck, wrap and pin the binding tape around the neckline. When you get to the ‘v’ cut a small “v” in the tape so it turns smoothly.

Hand stitch it in place through the shirt material and the back folds of the tape so it doesn’t show. Only tack the V down with one stitch, leaving an edge open for the decorative step.

At the back of the neck, tuck one end of the tape into the other and stitch it closed.

Next: Do the same with the armholes; wrap and stitch.

Last: Tuck the tape under the ’‘v” at the lowest point, tack it down and run it to where you want the accent (under the right armpit, according to the pictures) Stitch it in place.

hmm don’t listen to me… Blueroses instructions are much clearer.

ha ha @Unbroken You are a stitcher, I can tell.

I’m more of a shortcut pragmatist (born from making stage costumes on no budget)!

^Awesome sounds like fun. Maybe I should check that out at our local theater. Though we have budget problems for sure : P

Ok so secondary question then, do you think I will have problems with the extra stitching stretching with the fabric when I try to put it on/wear it? I’m afraid of it looking perfect and then I try it on and the thread snaps

Binding tape (you may also find it called bias tape) is by nature, a bit elastic. Do you know how to do a basic running stitch? That’s all you need to put it in place.

The gap between stitches plus the elasticity of the tape will hold strong.

@Blueroses and @Unbroken thanks so much for the help!

Since your shirt is a knit, it would help if, before cutting, you stitched on both sides of the cut line. This is to catch the knit stitches so they don’t unravel knits tend to be uncooperative that way. Then just wrap the bias tape around those edges and stitch in place. And wa-la cool cosplay outfit done by you.

didn’t even think about that! thanks @DaphneT :)

I really need to learn more sewing skills lol