What size is too small to penetrate?

[flynnno1000]

After some gentle anal experimentation with my boy, I don't think he'll be able to fit me comfortably, he may just be too small of a breed. And I definitely don't want to force anything on him, I want him as happy as can be.

What's your experience been if you've had any? Are there certain breeds that can accommodate you over others? What kind of breed would accommodate me?
And for reference, here's a few pics of me and one with my doggo

 

[nekdoneco123]

not that much anal experience on my part, first time i have a partner that enjoys it. he's a saint bernard, can fit me and then some with ease and i'm not that small...

you can try with just your finger and try working from there, if he does enjoy it. never force anything.