defensive posture

[Havoc]

In fact, any chance of you posting a pic, Havoc, demonstrating an ideal defensive line, as described?

Peter

There isn't an ideal defensive line as each situation and available terrain will dictate.  That said, I've attached some very simplistic set ups with few pieces as a flat defense (def 1) and a hill (def 2).  You might choose to have the tactical reserve battalions in line for better firepower against units that exploit break your main line to reach your guns, but then their ability to move up to counter will be effected. Cavalry can penetrate this line and reach the guns, but they will pay a price and will be disrupted in the final melee.

 If you are outgunned by artillery, reverse slope is not a bad option, with your battalions just below the contour line and skirmishers above to "see" and placing your available batteries a few hexes back with a clear shot at the crest.

Light guns are generally best 1-2 hexes behind the line, as their range is only 7-9 hexes.  Heavier guns with 11-15 you can stage farther back on hills.  In flat environments, you will be forced to keep clear firing lanes for your guns to be effective.  I will stack batteries with infantry in the first line if I can place them in villages, woods, or behind a hedge or wall.

Use skirmishers in the hexes in front of your line to force your opponent to use battalions to clear a path to your line. Cover screening skirmishers in the open with ZOC or one cavalry squadron could potentially "ride the line" and wipe out a whole row of them. 

Lanes between your battalions is often helpful for cavalry to counter charge without having to move battalions to make a hole and draw fire.  I tend to try to "mask" my cavalry by placing them behind guns, reserves or terrain to prevent them from drawing artillery fire that may disrupt them and prevent counter charges.  Also, breaking them down into squadrons prevents one hit from a gun battery from disrupting the whole formation.

All of this is obviously IMO, but I hope this helps.