Errr. Pardon?

he Rulebook examples include the NAC Phalanx which is big, but wheeled.
Look at a modern "big but wheeled" armoured vehicle, like the Italian
Centauro B1 (which is a "Tank Destroyer" that carries a 105mm tank gun
on
an 8 wheel chassis).  It has a weight in the 24,000kg class - half that
of
the tanks carrying the same gun - but you can carry it in much smaller
aircraft.

** With the exception of the AC-130, I don't think I've ever heard of an
aircraft carrying a 100mm plus cannon. 

  Maybe the wheeled NAC designs follow a similar design philosophy
- - they do have to be lugged around rather large areas of space,
afterall...
 The NSL and FSE vehicles are GEVs, so you can imagine the designers not
producing them with maxed out armour (and weight).

** SG2 isn't about cost. If you want to factor in design costs and trade
offs, use DS2 to design your SG2 vehicles. That'll give you some concept
of
why you might or might not want to do certain things. 

Thomas Barclay
Software UberMensch
xwave solutions
(613) 831-2018 x 3008