Something occurred to me the other day while pondering Deathwatch. How do space marines handle "handedness"? As a player of 40k since the first states side release of Rogue Trader (the war-game that started it all, not the more recent RPG), I've read the countless reiterations of the modification process that makes a normal man into a space marine. It came to mind that I don't recall any particular implant rewiring the brain pathways and/or genetic markers that control handedness (our actual scientific understanding of handedness is still being developed).
The reason it seems an interesting thought is that we see abundant examples of space marines dual wielding weapons to devastating effect (the ol' bolter and chainsword for example), but no real mention on how they learned to use both hands effectively enough to be able to shoot straight or hit hard enough with their "off" hand. This leads me to wonder if there is an implant process or hypno/psycho/indoctrination/training/brainwashing that addresses this and in essence makes all space marines effectively ambidextrous.
In most real-world applications, people tend to switch weapons out of their dominant hand rather than attempting to use both hands to fight (outside of hand to hand combat at any rate), don't let Hollywood fool you.
I wonder if the RPG will hit on this little detail.