It's always good to talk to someone who knows what he's on about, can tell you the pros and cons, but without being pushy. So thanks to Darren for good value and good advice
Here Darren is explaining to John the benefits of medium density foam, the curved and slightly raised edge, the buttons to keep its shape. Meanwhile John calculates the height and thickness of both foam and base. And that was before we started on the different fabrics, their "rubbability" and whether washable or dry cleanable.
There's more to this bench making / bed making lark than meets the eye.
However we've ended up with two parallel 19 inch high by 6ft 3 inches long benches, 2 feet deep, each with two back cushions, plus one folding table, which will provide us with either 2 narrow beds, 2 wider single beds or one double bed, depending on how we lay the cushions.
Here's the pattern we've chosen.
We start work tomorrow.