So you think of his girth as a challenge? That is good for a start!
I am not even close to the girth mentioned (I don't think it exists, but that is not the point), but I am rather thick.
So here is my advice, based on experience and common sense.
1. Decide if you like the guy enough to try and/or would like to try his size
2. Talk to him. Tell him you are really willing to try, but you never had anything close that thickness. Tell him that when you tell he must stop/pull back he immediately must do so. Tell him to be patient.
3. Make sure you are totally relaxed. Starting with probably a nice diner at your home, a movie or just some chatting and maybe a glass of wine. Sort some relaxing music in the back ground when you are working to the great moment
4. Make sure you have lube
5. Make sure you have a great foreplay. When you would want to loosen up probably tell him to use some fingers. Working up to 3, 4, maybe 5? Be sure his nails are short, and he is not wearing a ring. Maybe use some "tools"
6. Maybe upfront start using some "tools". Not to thick, but bigger than average
That's about it!
And of course for having this and other great advice. Make sure you measure, take pictures and reward us :wink: :wink: :wink: