My modified Tina shawl is constructed as follows:
The arrows illustrate the direction the knitting is worked in.
As you can see, the direction of the edging is perpendicular to the direction of charts 2 and 3. This fact becomes very important if you’re making a triangular shawl and you want all the top edges to line up. Because if you knit the edging repeat straight on to the main body of the shawl, without any modifications, the top of the edging will slant downward. Like so:
See what I mean? It might end up looking okay, but it’s not really the effect I’m going for.
I also can’t just follow the pattern’s instructions for corner edging. I know this because I tried. The instructions require that you attach an entire 16-row edging repeat to 4 corner stitches. I didn’t photograph my attempt to make this work, but trust me, it failed. It produced too much extra fabric, which just bunched up in a really unattractive way. I could have blocked it to flatten it out, but even then, the top of the edging wouldn’t have lined up the way I wanted it to.
So I broke out the pencil and knitter’s graph paper and re-worked the ends of the edging to include short rows. Swatching my new charts gave me these:
Neither is absolutely perfect, but they’re very close to what I’m looking for. With a couple of minor modifications, I should be good to go.