I believe the key to a good fit of this garment is the right cast on. The neck edge is designed comparatively wide, which is nice for a summer pullover. However, if the cast on is too loose, the weight of the piece can easily pull it open over time. I started with a German twisted cast on and frogged it again after it nearly came off my shoulder with some pulling at trying it on early. A simple long-tail cast-on did the job and keeps the neckline nicely in place now.
I had only 100g/800m of the mohair and went therefore for a cropped, short sleeved version. Still have a couple of grams left. If the length is not ok after blocking I might decide to add a couple of rows to the hem (which I worked as an overlapping split hem following the instructions in this nice video tutorial from Olga Putano). I worked the back side some rows longer instead of the proposed closed hem with short rows.
Lace pattern: My recommendation - swatch it and learn to read it, after all it’s only three different (rs) rows of 8-stitch repeats that are shifted by 4 stitches for the next repeat. If you can read it, no stitch markers needed and you can forget about the charts and just knit the pattern as far as your raglan increases allow, knit the remaining stitches. The charts can be misleading if you swatch flat as the starting double decrease should utilize a stitch from the previous repeat.