The motor I am currently using is 200 RPM and has 2.2 kgf/cm.

This motor is 280 RPM and has 5 kgf/cm:
https://www.servocity.com/280-rpm-pr...ary-gear-motor

This one is 350 RPM and has 5.7 kgf/cm:
https://www.servocity.com/350-rpm-pr...ary-gear-motor

But the servocity motors also say, " Gear train damage can occur if stalled (locked)." So if you stall out your tank by trying to go up too steep a grade or something you could damage the transmission. Probably true with any of these.

So, the servocity motors appear to offer over twice the torque of the uxcell motors I currently have. A redesign may be in order!

Steve