Does having two Best-craftsmanship bionic arms grant +20 to strength tests made with both arms?

Question

Dark Heresy Second Edition

Would each arm's +10 bonus to strength tests made using the arm stack with each other when using both arms to lift something?

Best craftsmanship bionic arms provide a +10 bonus on Agility tests requiring delicate manipulation and add a +10 bonus to Strength tests using the arm. They can be also used to store small items (such as pistol ammo clips) inside concealed interior compartments within the arm.

And would these bonuses apply to a Heft test, such as when carrying a heavy, two-handed gun and needing to increase max carrying weight to avoid being Encumbered when carrying it?

Heft
Athletes are also known for their strength and can lift great weights for short periods of time. As a Free Action, a character can make a Challenging (+0) Athletics skill test to increase his carrying capability for a single encounter. For every degree of success the character achieves, his Strength is increased by 10 for the purposes of how much weight he can carry, lift, or drag (see page 248), to a maximum modified Strength of 100. Hefting can only be attempted once, and if the character fails the test, he cannot try again until the next encounter.

Answer 1

I know that this question already has an accepted answer, but I looked a little deeper in the rulebook and found this, on page 180:

Note that the bonuses and penalties relate only to tests made using the bionic limb, and characters who possess two bionic limbs do not gain double the bonus, but rather they may apply the bonus regardless of which bionic limb they are using.

Though this is RAW, I would recommend discussing the matter with your GM. If s/he finds the rule to be unfair to gameplay, then you can change it.

Answer 2

I don't see why it wouldn't. There doesn't seem to be rules not allowing them to stack. Even logically, if you're lifting a really heavy object, two cranes can lift it easier than one.

So, if you are using both arms, you should be plenty capable of benefitting from both of them.

The exception might be where you get to using more than 2 bionic arms, because that can get pretty silly. Also, logically, there becomes a point where the rest of the body can't support the weight, even if the arms can.