Hi Bill,
I found the best way to cut the tank was with a sabre saw. Cut like butter.
For the the tank height I measured the tank taper od's at 1 inch intervals (tank manufacture tapers are different). Next decision, do I want the tank top at sitting height or reasonable capacity height? I opted for the later since Ric mentioned he would love to have more capacity. I then measured the largest diameter of the tank ('bout middle to the top 1/3 of the tank), and made my initial cut where the tank started to taper. Using the ods' (taken at the beginning), I then removed 6 inches from the initial cut (from the top part) which gave me a od to match the id of the bottom. I checked the fit, the top part now fit within the bottom of the tank extremely tight. And as a matter of fact, I could push the top part down within the bottom until the heavy rim on the top rested on the cut collar of bottom tank. Perfect butt height! Using pry bars I pried the two apart, removed another inch wide collar from the top, slid the top back within the bottom, still tight. As you cut material off the top, you're changing the od, so go slow! The two halves fit very tight, and you've got to use pry bars to separate the two halves, so there was no need for a silicone sealer. I used stainless screws, locknuts and fender washers to hold the two halves together. As you can see, its taller than butt height but still quite comfortable (with a pad
)!
Here in Flag I found the tanks (2 different sizes) at feed stores. Also, you might want to call auto dealers and car wash locations. Car wash soap comes in these tanks and they have them as well. BTW, I was going to add a separate lined rubbermaid tank within this tank (tank within a tank) but decided the benes' were not worth the trouble.
I also looked at the industrial rubbermaid trash cans, but they were too flimsy for me.
don