Research indicates that others have estimated the size of the maniple at about 160 men, consisting of two centuries of 80 men or the "reinforced" Maniple I described in my initial response.
This was the basic manuever unit of the Legion (about regiment-albeit a small regiment.)
The Manipular Legion was created By Camillus for flexibility in rough Italian terrain. The Phalanx was abandoned in Roman use.
The Legionaries were the heart of the Legion.
Without stirrups and more zest for riding than skill, the Cavalry arm of the Legion (800-100 bc) was poor.
The light infantry (veeiites or velites) were not bad.
A medium depth "T" stance is suitable for wielding the spear with both hands "underhand". This was done in the Major Macedonian Phalanx as their shields were affixed to their left arm and shoulder.
I cannot recall whether the Macedonian Army 0f 326 BC field any "normal" phalanxs armed with the eight foot dory.
The rank and file of the maniple was three "ranks" of 20-30 men wilh files of three.
Although the Hastati were named for the 6 foot "Hasta" thrusting spear, they formed the first line of heavy infantyr armed with two pila and a short sword. This was true of the second line (principes consisting of Legionary veterans) and the third ranked -the triarii was armed with the Hasta. The hasta is variously illustrated as being from 6 feet to 12 feet in length depending on the source. My leaning on this is toward the shorter spear, although this could have varied depending on the time frame, area of deployment and nature of the opponent..
One assumes the ranks were quickly reversed when the legion faced a heavy cavalry charge and the gaps between the maniples were closed.
The frontage of the maniple of the size given was about 20-25 yards as the swordsmen needed more room to employ their weapons than a Hoplite might. Hoplites have never been given high ratings, generally, as swordsmen, with indicates much time was spent in in the training of the Roman Legionarys, as the sword is more difficult to master.
In short, Sanchin is not a suitable stance in these situations and is not used in any of the fencing, straight sword, Bo or spear forms on which I worked.
Sometimes, In the Phalangial Legion, greaves were worn by some ranks, or some times worn on just the forward leg, obviating the necessity to turn the forward leg to allow the muscle to protect the shin. A slight turn, however, does not seem impracticable, however.