Actually, did the surface area math for a Timberwolf/Madcat mech years and years ago and they were (unexpectedly) fine.
They had something like 25% more surface area per foot than a challenger 2 does with both treads.
The bigger issues are that chicken walker legs don't work to support 60 some odd tons of weight, and that the 10-15m height is a little bIt too noticeable