Here is a thread from The Dog Brothers forum on bilateralism: http://dogbrothers.com/phpBB2/index.php?topic=513.0
No-one can deny that the left and the right side must work together, and if you can use your left and right hands/feet interchangeably, all the better.
Any usage of double weapons will require this ability.
There is some debate however, about whether you should train your dominant side to stay dominant - it's stronger and better already and should be as good as it possibly can be, or whether you should train the non dominant side more - until it gains the same facility (or as close as possible) as the dominant side.
Sonny used double weapon training, and also 2 handed weapon training with the Bogsai to improve the non dominant side, in my case the left side, but was of the mind that there was no need to force both sides to be equal, as long as they both worked, and both worked together, one side could be dominant. He referred to them as the husband and the wife, implying that if they were by nature different, but if they worked together, that was good, if they were at odds with one another it was bad.
So the question is - it is it desirable, or possible to be completely bilateral?
A couple insights I had when training my left (non dominant) side. These come from house painting.
I trained myself to paint with my left hand by moving both hands together, my right hand would do the motion at the same time as my left. After a while I noticed that as long as my right arm muscles were engaged even if they were not moving, my left could paint - this actually took a long time to get rid of and now I try to consciously relax my right side when I use my left.
(I transferred this to learning how to use the sword in each hand - Both at the same time and also, switching from right for a move and then to left to copy the move.)
After a while it felt as though my left was pretty much as good as my right at painting accurately and quickly ... until I got a bad bout of tendonitis in the back of my right hand that made it very hard to use at all.
I was forced to paint entirely with my left for a while and what I noticed was how hard it was, and how bad my alignments seemed to be, my whole body seemed twisted and awkward.
Took me a while to realize what was going on - Even when I had been painting with my left, I had been changing my brush over to my right as I dipped it in the can or moved around, so only one part of the action was being done with my left. I had been avoiding the rest of the motions for a reason ....
I realized that the whole body actually has to re-orient around the hand, AND THE EYE, to paint constantly with the other side - or dip, or move, pick up and carry.
I am left eye dominant, so painting with my right hand involves my body aligning in a certain way to get the left eye/right hand coordination needed to paint a straight line. Switch to my left, and the alignments change to left hand, left eye. If I could sight out of my right eye I could keep the mirror image of the alignments .... but that would involve changing how I look out of my head ......
Hmmmm, so the question is, do you have to sight out of each eye in turn depending on which hand is in play to achieve true bilateralism? Or is it just one thing that you are doing ... sighting out of a single eye and aligning your whole body around it - left or right?
And then the obvious next question comes from how using peripheral vision plays into left side/right side hand eye alignment to the target ..... (I am wondering whether using peripheral, and then not using sight at all, at contact range, the whole ball game changes, and bilateralism becomes much easier and more natural)