[jacobmuller]

you're using maths:0 UT page 227, Tank 30 ton SM+5...
But the maths solution is why I started using relative density for spaceships (the armour stats appear to assume an average density of around 0.7). And the same idea would apply to mecha - who says they float? But using that amount of detail would take this thread off into the twilight zone.

I like VMs ideas and didn't intend to sidestep them. I guess the SM difference is best assumed to balance out.
Re OP armour: I went even simpler but used Spaceships, eg 15 systems of armour, divide by 3 = average armour; Head & Torso/ Limbs 0.42/ 0.29. Add in enhanced survivability and higher density = lower area. But that's all more maths. LOL