Yeah go for magnum XL. I'm ~1.5cm less in girth and the XLs fit me alright, but I'm uncut so I like the extra tightness of the standard magnum to hold things in place better.
I was really apprehensive about buying those things at first, because way too many guys (many who don't need them) just get them to stroke their own ego and make sex all about their own dick, instead of about two people having an awesome time together. I didn't want to be one of those guys, but after having several Durex ultra-thins snap on me in less than a week, it was just crazy not to. Waiting a month to find out if two separate girls I was just friends with were pregnant, then getting STD tested again, is not an experience I'd care to repeat.