Chose this pattern because I wanted to make the right one ‘convertible’ so that it’s as practical as possible for taking photos, holding bus pass, blowing my nose!
Being top-down, I could better gauge where my opening was going to be. PLUS loved the fact that I could base it on my own gauge and measurements as had frogged too many times with other patterns. These needed to be as warm as possible as a single layer mitten. I live in the Arctic…
Have used Techknitter’s Tulip buttonhole as opening. My first try.
Am knitting on 5.5mm needles, used 3.5 dpn for buttonhole opening, and it was fine, not too tight. Also made buttonhole for thumb to pop out of.
Should have done my cast-off stitches tighter.
Still awaiting testing.

Update: the openings work really well. I can use my fingers without taking mitten off, which is exactly what i wanted.
I might add a flap on hand opening that i can tuck in for extra warmth.
Am not happy with absence of ribbing at cuff.