Ed,
didn't quite understand the notation 1/3
Squadrons would not have charged in a single rank. Can't give a precise figure for that maybe someone else could.
As for regiments charging.. originally in the WHC rules when I first saw them way back in 1990 cavalry charged in a single rank of 10-12 figures. This was a bit clumsy and also a bit ALL or nothing. I dev eloped the idea to allow them to charge in squadrons (thus the do I don't I decisions about feeding into a winning/losing melee situation became more significant).
In my adaptation of ULB into the Napoleonic period(Republic to Empire) I have allowed the option for multi squadron regiments to charge ALL squadrons at once in a sort of 'decisive moment' charge. I may add this option into ULB but my main rationale for leaving it out in the first place was that I felt the cavalry of the earlier period may not have had the training or discipline of those in the later period and perhaps were not as well suited to a well coordinated regimental level charge.
I am challenging myself as I write this and thinking maybe a contra agrument could be used .. in the earlier period the less sophisticated training levels may have compelled an all or nothing charge by the entire regiment.... hmmmm
Comments would be welcome from both students of Napoleonic warfare and that of the 17th century..