"I haven't figured out how I'm going to ask yet." Which was a total and complete lie. He'd thought about it and thought about it again and had come up with about ten different ways that he could do it. His current favorite involved a Mudblood captive and a grizzly version of the stereotypical engagement ring tucked cleverly into a little cake ruse.
"Of course you'll have to be my best man." There really wasn't anyone else he could turn to for that, he didn't have any friends and he knew Rabastan would do anything for the honor.