I see most people are using 4 inch wide flexwatt here for their 38 and 41 quart tubs. This apparently works, and there is no argument with success. However, it just makes no sense to me whatsoever. I would like to understand why people do that.

The common recommendation sometimes by the same people are that the hot spot should be 1/3 or so the area of the tub. That would mean that the tub suitable for 4 inch would be only 12 inches long. It is even more strange that many people use all 4 inch flexwatt for DIFFERENT SIZE TUBS. I read one post where they used 4 inch heat tape for ALL their racks, hatchling to adult.

I myself use 11 inch heat tape (not flexwatt, but living in Asia we use a different brand that is rated the same wattage per foot as the flexwatt 11 inch, and is 220V electrical system which suits us here.) for my tubs which are 21 inches long on the bottom and 24 inches at the top. I slide the tubs back only so far that there is some space at the back and 7 inches are under the tub. This is because there is no 7 inch wide available, but I just can't see 4 inches as optimal. For my smaller rack (they use tubs that are about the size of your 16 quarts, and are 15 inches long or so), I use the same 11 inch but use it lengthwise (so the wires are coming out from the back of the rack, it is a single column rack) and cut them so that they are 5.5 inches long, only because I leave about half an inch at the back where I don't slide the tubs back all the way. The tubs are also 9 inches wide and thus fit well this way as far as width.

All of them thus have exactly 1/3 of the tub which has heat under it. The reason I use the 11 inch and cut it like this is because my friend ordered a 100 foot roll of that heat tape and we shared it, and it seems to be working well. My friend successfully bred last year as well.

Now, I understand that heat "dissipates" over a wider area, but unless you are using a heat distributing surface like that they have in ARS racks metal plate, that hot strip is going to be hotter than either side for sure, and for snakes that are in a 38 or 41 quart tub, they are big enough that they would not fit into the 4 inch area coiled up for sure. This just seems really strange to me. I saw some people in the west even decide to put two 3 inch pieces beside each other because they felt the same way.

Can someone explain why? I mean, if they sold 5 inch, 6 inch 7 inch, 8 inch, chances are you won't use the 4 inch for everything, am I right?