The first thing I noticed was the decrease row between the two charts. First you knit a regular increase row, than a plain knit row, then a decrease row where you decrease 8 stitches, another knit row and then start knitting chart 2. As I started working the math, the first thing I noticed was that if I did my increase row I would end up with 291 body stitches, while the chart needs 280 for the circular version and 281 for the flat version - remembering that extra stitch at the end of the row. That meant that I would have 10 extra stitches. My first thought was to take advantage of the fact that I could work an extra half repeat of the chart. I fired up my charting software and first entered the chart as written, then I started adding columns and copying and pasting, expanding the chart in both directions. As I worked I pondered the implications if I were to keep those 291 stitches on working the rest of the shawl and decided that the best course of action would be to maintain the stitch count as nearly as possible. I also noted that there was a very simple way of making this chart work perfectly for knitting flat.
The solution was so simple that I wondered why the designer didn't adjust the chart during the design process. All it requires is a little arts and crafts. First, print the chart, then cut the chart vertically between stitches 15 and 16. Also trim away the "no stitch" in column 21, cutting carefully around the 3 stitches in rows 47, 48, 49. Now take that strip of stitches and place them to the right of stitch 1, carefully lining things up and placing those 3 stitches into the no stitch section of column 1. Apply tape to secure. When you knit the chart, there will still be an extra stitch at the end/beginning of the right side/wrong side rows. Just knit/purl that stitch as appropriate. On rows 33 and 53 that stitch is needed to handle the s1k2togpsso stitch as it was handled in chart 1.
Pattern: Evenstar Shawl by Susan Pandorf, converted into a cape
Yarn: The Unique Sheep Eos in Midnight Delight
Needle: US 3 (3.25 mm)