Ann, maybe it's an indoor/outdoor thing?
Mom's Shelties LOVE the "cot" beds, the ones made of PVC pipe and mesh. However, her dogs spend the days outside in gravel pens (when the weather is nice), and so the cots a) keep them from having to lay on the stones and b) provide airflow underneath.
Inside the house, she has an assortment of regular, "poufy" dog beds, which the dogs also like (but different dogs like different beds more than others). I have no idea if the dogs would choose a cot in lieu of the poufs, if one was brought inside.
I have had dogs who just aren't fond of beds, and dogs who needed a bed in every room so they could go from pouf to pouf. Sheep, since Spitfire is an all-indoor dog, perhaps you could start with a softer bed (instead of a cot) and see if he likes it. Even though it is hot right now, it just gives him another lounging option.
Yep kind of wondering if Spitfire would trust it.
Funny story: when I first had Betty Cocker, I splurged and bought her a big, round pouf from Orvis. (I LOVE this bed; it is made tough and is very washable - yes, I paid more, but it's built to last.) When it first arrived, she wouldn't go near it! I would toss cookies onto it, and she'd oblige, but then hop right back off. It was very disappointing.
Fast-forward a few months, and Mr. Tofupup and I are getting ready to move halfway across the country. As our time there wound down, we were getting rid of things we weren't going to take along... in particular, the hand-me-down sofa. With no sofa to sit on, I started sitting on the dog's bed in the evenings (because she sure wasn't using it.)
Wouldn't you know it, after I had sat/laid/lounged on that big dog bed for a few evenings, Betty Cocker decided that it was awfully nice! She loves her bed now.
So Sheep, maybe Spitfire will just need to you provide a demonstration!