I'm a roll around while I sleep kinda guy, but mostly I'm a side/stomach sleeper, and often with one knee up. I have to balance myself carefully on a 20" wide pad to keep most of my body on it. I'm currently using a big agnes rectangular bag/pad combo (long), and I fit in it pretty nice. I know it's not the lightest - pad + bag is 5lbs, but for the weight, there's nothing that comes close to its girth dimensions, and I got it on a screaming deal.
I'm 6'2" and 225lbs at the moment (hope to drop that down a bit) and wear xl-tall or 2xl, depending on the garment.
I'm gearing up to give bike-packing a try- looks like a lot of fun as I'm an avid mountain-biker, so bulk is a big issue, which is what is motivating me to look into making a light 40 degree-ish down 3 season (SoCal desert seasons) quilt. There no way on God's green earth that at any time in the foreseeable future I'll be shelling out $400 or more on a sul down bag.