What do people recommend? I am thinking a self inflating mattress on the stretcher, plus a sleeping bag, but am now wondering about adding a blanket on top of the mattress as well as over the sleeping bag. He is a big guy, so I am hope he copes with the bag ok.
This is not a light weight solution by any stretch of the imagination, but it is the most comfortable I've ever been while camping, very close to as comfortable as a good bed really.
I have a King Goanna stretcher. Since you note he is a big guy I'd recommend this, it is SOLID, also longer and wider than most. I'm 6'5 and around have slept on it when I was 120kg without a trace of give. *Cough* It can take two without any give */cough* Weighs about 20kg and takes up around as much room as a camp chair when folded. It was around $120
On top of it I have my swag. I had a mattress custom made for it to replace the standard foam mattress. It is comprised of a layer of latex with two layers of foam with different densities. The softer layer is around normal swag foam in density it is around 75mm thick total, 50mm latex, 15mm soft and 10mm dense. It was $290, weighs around 20kg as well. The place that I got it made (a local mattress manufacturer) came up with a 3 layer foam option that was almost as good for $140 and it was much lighter, only slightly heavier than a normal swag. I knew the owner and spent some time out the back with him trying out different combinations of foam densities and materials that we could fit into the available space. Can't quite remember the exact densities of the foam we figured out were "best".
I have a normal cotton sheet on the swag and almost always sleep under my sleeping bag (0 degree) unzipped and used as a doona. It's comfortable for a range between 0 and 20 degrees, at the lower end of that a light wool blanket under the sheet helps. -10-0 I sleep with the bag closed. Above that I just have a sheet.
If he is really big get him one of the King sized (I think there might be a Super-King). I could get in mine at 150kg, didn't have much room to move though but the newer bags are actually larger than mine.
I wouldn't want to lug it around at close to 40kg and not a small footprint but as I rarely go further than the wheels will take me, it is perfect.