I dug up some reference from the old eia FAQ that seems dead on topic:
3.1 Monster Stacks
One tactic tried by many players is the use of "monster stacks." These
are stacks of as many corps as you can put together. The theory is that
the loss of leader tactical rating doesn't hurt that much, and you will
inflict terrible losses on the enemy, even if you lose the battle. After
one or two battles with such a stack, the enemy will have few troops left
with which to defend.
Many players feel that this tactic can be overcome by attacking the
nation with the monster stack where it is lightly defended. They reason
that, if the majority of the army is concentrated in one stack, many
provincial and minor country capitals are left undefended. By capturing
those capitals, you can force the monster stack to disperse to defend
holdings.
Other players feel that the monster stack is ahistorical and detracts
so much from the game that they have written house rules to prevent it.
Some are given below:
3.1.1 Peter Lodewyckx
peter-L@tornado.be
We have the following house rule:
1. Stacking in an area (regardless if combat occurs or not) is strictly
limited to
a. Corps with leader: 2 times maximal corps rating -1WITH a minimum of 2.
This means a leader can never have more than a -1 on his tactical rating
(unless reinforced, see below). Example: Nappie (5.5.6) can command 6 corps
(5.5.6) or 6 to 11 corps (5.4.6). There cannot be more than 11 corps in the
area with Napoleon. Even Jerome (2.2.1) can command 2 corps.
b. Corps without a leader: All corps can stack with ONE other corps. Being
stacked does affect their Tactical Rating by -1. So it becomes _1_ for FR,
GB, and
late PR corps and _0_ for all other.
2. This can only be violated due to reinforcement in combat. If a successful
reinforcement occurs the commanding generals tactical rating can go
(further) down due to excess corps. Example: Nappie (10 corps) is reinforced
by Jerome (2 corps) then Nappie (in charge being A-class) goes from (5.4.6) to
(5.3.6) after the reinforcement.
3. If after combat there is an excess number of corps present in an area
(due to successful reinforcements) the OWNING player must retreat the
appropriate number of corps according to the normal retreat rules (to supply
source etc...).
We have playtested this is a grand campaign game (we are currently in 1813)
and it works just fine:
1. You get more "historical" feeling (no I will not re-start the discussion
of Simulation versus Game

): Marching Your stacks apart and concentrating
on the enemy.
2. You use all Your leaders (not just Davout and Napoleon, even the Grand
Vizir and Alexander become interesting with their high maximal ratings)
3. No "Free forage" with the entire French army in an area that hardly can
accommodate that many soldiers, let alone feed them !
3.1.2 David S Ammerman
xportr@ix.netcom.com
1) The maximum # of corps allowed in an area (without penalty-see below)
is determined by totaling the corps capacity of the TWO highest corp
capacity leaders in the area.
EXAMPLES: Napoleon, Soult, and Jerome are in an area. Total corps
capacity would be 6 (Nappy) + 3 (Soult) for a total of 9 corps.
Charles and Kutuzov are stacked with an allied army. 6 (Charles) + 4
(Kutuzov = 10 corps capacity.
2) ONE cavalry corps may always freely stack with other corps at NO
penalty.
2a) A cavalry leader allows a # of CAV corps equal to his tactical
rating, to stack freely with a stack. This is in addition to all other
considerations.
3a) Corps with 10 or less factor capacity count as 1/2 corps for stacking
limits purposes (example: Russian 4th inf corps, Bosnian Feudal infantry
corps).
3b) Corps with 21 or greater capacity count as 1+ 1/2 corps for stacking
limits purposes (example: French Guard corps, Prussian I corps).
3c) Cossacks, Guerrillas and Freicorps may always freely stack with corps
at no penalty.
4)Leadership ratings apply. The highest rated leaders in the area must be
used for counting corps capacity totals ( we use a special rule which
says that Bleucher is promoted to a "B" leader in 1807).
5) Reinforcement: Reinforcing a battle may exceed the corps capacity
total for an army. When this happens, a "-1" is applied PER CORPS (1/2
corps count as 1 if reinforcing alone) against the tactical rating of the
commander in charge of the battle. Thus if Charles and 6 corps capacity
are in an area and reinforced by 2 additional corps capacity, Charles'
tactical rating drops from 4 to 2. If Charles were further reinforced the
next round with 3 additional corps capacity, Charles' tactical rating
would be "0". Once the leading commanders' tactical rating reaches "0",
no further reinforcement may take place. If, as a result of
reinforcement, more corps are in the area than allowed, the over-stacked
corps must retreat IMMEDIATELY to the area they reinforced from.
5a) Exception: If the reinforcing force introduces a new commander that
can be counted for maximum corp capacity purposes, the total # of corps
allowed is recalculated immediately.
Example: Pechlivan Khan and Kushanz Ali are in an area with a total of 6
corps capacity. They are reinforced by the Grand Vizier with 1 corps
capacity. Since the Grand Vizier outranks the others, his corps capacity
must be used to calculate the total allowed. While this increases the
maximum total to 7 corps (and thus no penalty), The Grand Vizier takes
command!(Yuck)
Thus, leaders used for reinforcing must be used carefully, lest they
affect the maximum possible corps and/or take charge of the battle.
Still another tactic, which requires some luck, is to form a large army
(tempting to the monster stack) under a leader with a high strategic
rating. Withdraw each time the monster stack attacks. Eventually, the
monster stack will choose escalated assault to get the -1 DRM to your
withdrawal roll. If you time it right, you can outflank or defend,
probably inflicting severe losses.
If optional rule 12.3.1 Supply Limit Per Depot is used, at least the supply of
the monster stack will be made more expensive.