I don't have their big tub rack, but I'm pleased with the 4 level combo 375 rack I have. It does the small hatchling tubs and the medium 28 qt equivalent tubs.
My biggest concern in the adult rack personally is that 3" heat tape doesn't seem like enough of a hot spot for large adults. Personally I would want either 6" or 11/12" heat tape on a tub that is about 3 foot long.
I know plenty of people use the small heat tape in racks without issue, so that may just be me being picky. I'm not too sure how well back heat works in general or the side heat, so that may actually be a better way to do it if you measure temps the right way for it.
I would suggest if your house ever drops below 75 in the room you plan to keep it that you get the enclosed rack, not the economy, unless you plan to run ambient heating with a radiant heater or something. This is true for any brand, though.
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