This is probably another of those obvious ones, but once again for clarity's sake.
Does the mass of handheld weapons (TO pg 316) get added to the mass of any unprotected cargo carried (TW page 261) or mech jump packs (TO 293)? Handheld weapons are limited to 10% of the unit's total mass and don't modify MP of the carrying unit, whereas unprotected cargo and jump packs can mass as much as the carrying unit, but impose mp penalties when their mass exceeds 10% of the unit's mass. Thus the question is whether the two items stack for the purposes of MP reduction.
For example, a hypothetical wasp is carrying a two ton handheld weapon and wearing a two ton external jump pack. Does this mean the wasp takes no movement penalty (because neither fashion accessory generates an mp penalty on its own), or does it take the movement penalty, since the two items combined total four tons and thus exceeds the 10% limit?