Mods
Top decreasing - after the first 3 rows, I added another row of straight knitting before doing the row of decreases. I also deleted the 12th and 14th row of knitting to get a more rounded top.
Thumb - pick up 15 live sts and then picked up two more that were immediately decreased into the first and last live sts that were picked up. Knit 12 rounds, then begin decreasing with round 13 in the pattern.

12.13.15: Finally completed. Took a long time on the second one because I didn’t know how I wanted the first one to be completed at the top. Made small modifications but overall followed the pattern as written. Also modified the thumb a bit.

Last photo inudes the mitten blockers I used to shape the mittens while drying. They worked very well!