I've slowing been working my way up in 'girth' with my dildos. Recently I've gone from 1 1/4ths to 1 3/8ths.
And while I can get it in, there is a pinch, at the very base of my vaginal opening, where the thin skin gets pulled taught by the silicone. The toy I'm using Mark.
I make sure I'm in the mood, I use lots of lube, which helps, but I'm just trying to get even a vague idea on how long it will take my body to adjust and get it.