This is my second cycle using the Lunette cup size 1, and I cannot, for the life of me, get this cup to open properly while sitting on the toilet. Although, when I lay on the floor on my back, I can slide it in and it pops open completely on the first try. Yet when on the toilet, I can still feel a dent when I run my finger around it and it never feels sealed. If I think it's good while on the toilet, then I lay down on the floor to make sure, pull my legs up and I hear the whoosh of air signaling its opened completely and sealed.
I have a really high cervix (the cup AND stem pretty much disappear after a while of wearing it). I really don't want this to be my only option of getting it to seal properly as that is really awkward in public or at other people's houses. I've tried angling my body in all kinds of directions on the toilet, but I never hear the "sealing air" sound until I lay on my back.