What kind of dimensions would that be? 7&1/2 girth? 7 length or over?
So, perhaps this is a good example of someone with the burden of such a fat cock that few women can take it in their mouth and possibly in their pussy (at least, comfortably). Aside from the massive ego boost he'd get when whopping it out, it's probably quite disappointing if he can't get the full blowjob to completion.