[Rupert]

I'm tending towards the rule from The Path of Cunning, combined with the reduction in damage for attacks vs very large targets from Keeping Large Vehicles Alive (Pyramid 3-34, Eidetic Memory) which I would also consider applying to Tight-Beam Burning attacks, treating them as if they are impaling.

Also, Spaceships gives ships about 50% more dHP than you'd expect from their mass (i.e. it moves them one step larger on the Range/Speed table, which is the progression it uses for dHP). I take that as being a reflection of compartmentalisation, etc. and am considering a similar bonus to any vehicle that has features such as good compartmentalisation, trained damage control crews, vehicle-wide automatic fire suppression, and so on.

It's possible all three of these measures together swings too far the other way, and the second measure won't stop giant mecha with swords carving each other up very quickly.