Hi all - I'm really not the DIY type and frequently it's preferable for me to buy a commercial product that's more or less ready to go with just some minor assembly. To that end, I've been looking at AP and Reptile Basics commercial racks. If I recall all I've seen, they each would come with 4" belly heat option. But in one rack I was looking at, the tub dimensions were 16 x 24 x 6 inches (rounded up). Is 4" flex watt sufficient floor coverage for a tub of that dimension? And then the larger size was 18 x 34 x 5 inches (again, rounded) with 4" flex watt for belly heat. In both those options, isn't that a pretty narrow band of heat relative to the floor dimensions? How do you provide an adequate hot spot for "basking" in such a small 4" strip relative to the floor space of the tub? All options I am considering would be back/sides enclosed for better heat retention. (Am I making sense? I thought there was some rule of thumb about covering some ratio of your tub floor for belly heat, and it was way more than what would be provided in these examples?)

Thanks much!