The over thing for consideration is you mention that you want a single swag and a swag that the young bloke can take into adulthood and have for many years.
I would ditch the single idea and get a swag for single use of around the 1100-1200 mm wide and may be termed a double. That extra bit of room can make the use so much nicer.
And for the alternative perspective....
The wife and I shared her single (900 wide) Darche swag on a 4wding trip over the weekend and we agreed how comfortable it was with both of us in there.
I would say we're both about average build (my beer guts are about as averagly big as other blokes beer guts
), but we didn't feel cramped in there at all.
I still have the old style fold over no hoops swag, but it really doesn't get used at all these days.
I was considering getting a new one at some stage and was thinking the 1100-1200mm wide ones would be better, but after our last trip I would only go with a single.
In my opinion the extra bulk in pack up size isn't really needed for comfortable sleeping. Not for me anyway.
