I've not had occasion to use on of these for our cats, as Paddy always preferred to snuggle right up against the radiator in his latter years, but I do know of people who use them for their dogs as well as their cats, and report having very happy pets as a result.
I hope you can get something suitable for your lovely Maine Coon lady, bless her paws. I can imagine how much it would make movement painful for her, having arthritis and being a larger boned cat.