So I stumbled on this in a reddit post http://www.fitmytent.com/ It is pretty awesome. It confirms that at least one of my tents has plenty of room, which I already knew. Before purchasing it I wish this tool was available though.

For the record I own a Durston Xmid 2 and Hyperlite Mountain Gear Ultamid 2 (with full insert). I’m 6’2” tall and have an Xtherm long/wide. So if it’s winter and I’m using my 6°F bag it takes up far more room than the average Joe.

Cheers!