I put the swarovskis on my Leica's, just stretched them over they fit in the gap when the original pull out eyecups are extended.
I look through glasses many hours a day for months during my hunting seasons for clients while scouting trophies for them. The fatigue from peripheral light, and wind takes it toll on long days of glassing. With the winged eyecups there is a very noticeable reduction in fatigue and increase in comfort. The wind is even more a struggle many days then the light.
I've used Leica trinovids the best glasses I've ever used for 15 years or more. But they were far more fatiguing before the eyecups. Then after.