Here's what we did:
http://www.tnttt.com/viewtopic.php?f=42&t=49766#p925635
Here's a link to the Euro military surplus cots:
https://colemans.com/cot-euro-militaryI was going to purchase them just for the heavy duty frames, and have a upholstery shop recover them with denier nylon. To my surprise the treated burlap was so strong and comfortable, I used them as-is. They have been going strong nearly 7 years now. Funny thing is now that the kids are grown, we sleep in them now, and they are amazingly comfortable. I can't find it now, but recall seeing a 300LB rating on these cots. I'm sure the welded tubing and legs will support it, and after all this time, think the burlap surface will too. In some of the closeups you can see the heavy gauge wire sewn around the perimeter, and the multitude of hangers, which spread the load out around the tubing frame.
With all that said, I might not put a 300LB fellow in my top bunk, since I have them partially supported by the ceiling members, but there have been multiple kids playing, climbing, swinging on them over the years, and our boats live there when they aren't in the water. Another fun feature is I can rotate the upper bunks up against the wall, and unclip the hanger from the ceiling e-track and move it to the upper wall e-track, pull the strap, and presto, upper bunks are out of the way for loading larger stuff. The bottom bunks still use the legs, and when not in use, they hang on the vertical e-track with two J-clips,resting just above the floor, rock solid and out of the way.
and a more recent discussion:
http://www.tnttt.com/viewtopic.php?f=42&t=71161&start=15