I just received my Fling today. I normally consider myself to have a smaller-than-average vag - for example, I recently had to totally give up on a dildo (the Jollies Jollet) that was firm silicone and 1.8" in diameter because it just wouldn't fit inside me. Every time I tried, I encountered intense pain and had to stop, even with tons of lube.
The Fling, for some reason, is different. I lubed it up and it hurt a tiny bit as I pushed it in, but then it slid right in and nestled comfortably inside me. I had no issues with it.
I think the difference is that the Fling's bulb is rounded and its neck is much thinner. This means that the pain and strain of inserting the thickness only lasts for a few seconds, and then it's in. (The deeper part of the vagina can handle more girth than the opening can.)
Hope that helps!