Spring Sleep wear - producing a simple pattern for t-shirts

For Spring sleep wear I have to produce 5x t-shirts & 5x bottoms.

I am going to start by producing 5 simple t-shirts.

As in the past with t-shirt type projects I’ve chosen t-shirts that have fitted me well & cut them up.

With this long sleeve t-shirt I cut away the seams leaving with just the “worn part” of the fabric, but before I cut up I mark on the fabric with stitches where the various pieces match up (& where there are gathers) so its easier to reproduce with the new fabric.

See the below pictures - before cutting & after cutting.

The grey thread on the sleeve matches up with the grey thread on the front &  back sections of the t-shirt (the extra grey thread shows that this is the back) The orange thread is on the seam of the front & back of the body of the t-shirt.

Let me know if this doesn't make sense!