This is where I am now.
I am making mine on Size 7 needles to meet gauge. But I wanted mine slightly smaller than the original pattern, so I did 61 instead of 71 repeats of the lace edging. Picking up stitches into YO loops took much longer than I expected. Some of my loops were obvious and some were not. Had 248 YOs [2 + 244 (61 x 4) + 2] and picked up 251 stitches (increasing 3 in middle 4 stitches as suggested). I realized that I needed to do just 4 sets of the two garter stitch rows (a total of 16 stitches decreased) to get the correct stitch count to start the Rock Island chart. After these rows I had 235 stitches to start Rock Island chart. I followed the chart as written except did the 6 stitch repeat 14 times (instead of 17). I messed up the Rock Island chart a few times early on and had to redo those rows. I then highlighted the SSKs and soon memorized the pattern. After that, it was smooth sailing. I have since finished the Rock Island chart and am slowly working my way through the garter stitch decrease rows. I have about 40 more rows to go. Can't wait to finish and block. This shawl is BEAUTIFUL after blocking.