Seon, I understand about the need for a trailer on hilly property, you can build it with a low center of gravity and a wide axle for safety, I hope you have luck finding a tank locally that shipping is expensive.
Npaden, I made the frame from left over angle I had around. The only thing I had to buy was two cat 1 pins $4. It took two partial days to build, one day to cut, grind, and bevel all the pieces and the next to weld, prime, and paint.
Scott