I'll add that a man is a bit more flexible and conforming than a hard plastic dilator (well, at least for the purposes of this conversation, perhaps not when it comes to things like ego and relationships!). So that should help.
Also, there should be plenty of ways to explain things to a man - "I'm fairly tight and don't want to get hurt, so go easy" should do it...if they can't listen at least a little bit to your desires, they probably aren't very decent of a guy. I'd also say that, as a guy, if a woman tells me what makes her feel good, and things I can do to accommodate her, I appreciate it. We don't naturally know what feels good to any given woman, and we're a bit dense, so sometimes a little help is nice.
You might also do things the first time on top, so you have more control over things until you know how things are working for you. You can make it a game - get the guy all worked up and then tell him, "Okay, I'll keep making you feel nice, unless you move - you've got to be still! The minute you move, we're done. We'll see if you can handle me!"
