Vehicular Tolerances FUBAR?

Burning Empires p. 596:
For the Maimed result, subtract the Forte exponent from the Mortal Wound tolerance.

While this may be a simple, expedient way to figure wound tolerances, I see two problems with it:

1.] It means that “stronger” characters are more easily Injured, but less easily Maimed than “tougher” ones.

For example, if we take Luke (Power 3, Forte 3) and give him the mutant grow formula to make him massive size, he will have the following tolerances: Superficial: B3; Injured: B6; Maimed: V6; Mortal: V9.

But if we give the same mutant grow formula to Dro (Power 3 or 4?, Forte 9), he will have different tolerances: Superficial: B9; Injured: V2; Maimed: V3; Mortal: V12.

Massive Dro is supposed to be tougher than Massive Luke, but Luke can get off with being merely Injured after taking a direct hit from a Nail Launcher, while Dro is always Maimed.

While I admit that this is perhaps a minor quibble, I would think that the tougher creature should not be penalized by having such a low Maimed Tolerance.

2.] The second problem is that it is broken! When I decide to create a giant tuber-like worm that has grown fat and lazy after becoming too tough for predators, it breaks down. The worm has Power 5, Forte 10, and of course is of massive size. It has the following tolerances.
Superficial: B10
Injured: V4
Maimed: V3
Mortal: V13

So… does it just never get Injured? or what?

Hm. Where did that particular artifact come from?

Until further notice, just use the standard method for figuring tolerances: Maimed=Mortal minus 2.