I have one and can't fault it. Doesn't slip, is warm yet breathable, keeps the rain off without being crinkly and is very bright even after 4 years or so of wearing and washing
I would get their largest size for that one - maybe ask them? I think I have the full size for my 16.1 6'3 to 6'6 rug wearing horse, but think they might have bigger?
I had an extra deep one made for a similar tank and at no extra charge! It was about 5 years ago so they may charge now, rug is still going strong, they are brilliant!