[mike31154]

Provided you use enough of them to distribute the weight of the system adequately for the strength of your floor, you'll be ok. As far as how many are enough, that's a tough question to answer on a forum like this without additional information on the structure the whole shebang is going to sit on. I would certainly confirm whether there is a metal disc inside the lower plastic part of these adjusters. I assume the outer plastic portion is there to get a grip for easy adjustment, but with substantial weight on there, that could be difficult to impossible without breaking it. That's an assumption though, so I'm not sure I'd risk it without knowing for sure there's a good metal flange attached to the threaded portion.

As far as threads supporting the weight, that's an engineering problem really and you need to know the metal strength, quality, weight that each one will need to support etc. Having said that, I worked on aircraft for many years and one of the old jets I worked on only had 4 large bolts on each side to hold the wings on. These things were capable withstanding G forces of at least 6 positive and 3 negative. This is more for the pilot, since they tend to black out. From a design perspective the bolts would have to withstand more than that, for flight safety and longevity. Needless to say, this hardware undergoes strict quality control processes and is not your average stuff from the hardware store.

Use an item like this, manufactured under a global conglomerate for ordinary furniture to support the substantial weight of a large tank at your own risk...