If I could make the choice of how big my partners willie will b - it will be 20cm. Thats the best size in my opinion, looks amazing an still easily manageable. I cant help it, there's just some natural attraction to huge erections.
The biggest I had was about 25cm ( 10 inch I think) and I enjoyed
But have to say u need to be relaxed and in a very horny mood to make it fit otherwise can b little tricky
And also when the cock is lightly bended in the right direction it can do his job without enormous size.
Good luck that pussys r stretchy so they can adapt-customize and at the end of the day every cock will do and provide it's own unique pleasure