Split off the tangent on feint raised above:
http://www.ironcrown.com/ICEforums/index.php?topic=10633.0
Generally, it seems in the real world TWC was used either in the "Full DB left hand/full OB right hand" way, which the rules specifically stop, for good reason since it abuses the way RM combat works as a simulation. . .or it was used as a way to expand the potential for feinting, since the defender not only has to cover all possible motions of one weapon, but two possible vectors for attack. That said, in the end, only one opening comes up, and only one blow is struck with one weapon.
There are issues with getting too detailed in breaking out what you're doing during a melee attack, which makes me wonder if the idea of "TWC makes it harder for the defender to cover" isn't already in the system, essentially the parry rules for two handed weapons.
Say something like:
Both weapons use the TWC skill or the lower of the two skills (depending on which version of RM you're using).
VS Two foes
-20 to skill, TWC attacker must declare which weapon is directed to which foe, resolve as normal. Parry DB is gained in full vs both foes. (Or perhaps split, or raise the -20 penalty).
VS One attacker.
Declare the OB/DB split as normal from this skill, the TWC attacker only gets this parry DB once, not doubled
Any parry DB declared by a single target of TWC is halved to reflect the increased difficulty of covering two potential attacks.
If the two weapons differ in any way, when rolling the attack, an odd UM attack roll means the primary hand weapon is making the attack, an even UM attack roll means the secondary weapon is making the attack.
Reflects the fact TWC is harder to parry using a mechanism already in use for another context, and also the fact that the TWC attacker is using two weapons in order to increase their number of openings, but still only exploiting the best one that comes up, not making two attacks per declaration.