In some respects, my basing for 10mm / 12mm figures has to have regard for my 4" (100mm) Hexon II system from Kallistra, who in turn support their own 12mm figure line by supplying 40mm x 20mm plastic bases in the unit blister packs. I like their figures and have looked at whether this default position of a 40mm base the most practical?

For pre mechanised forces, in an effort to visually get a formation that looks like it is line while sitting in a 100mm hex, the unit needs something with a frontage between 80 - 90mm for cavalry and infantry, while artillery on two 30mm bases (total 60mm) looks fine. It needs to be remembered that often terrain (such as buildings and woods) and figures will need to co-exist in the same hex.

To get this overall frontage, I have tried 2 x 40mm bases, a single large 80mm base and 3 x 30mm bases, each with two ranks of infantry on them. There are advantages and disadvantages to each of the base sizes. 

The 3 x 30mm bases look good in march column, but in attack column, they need a 4th base adding to look right (to give a 4 x 4 configuration). It also increases the amount of base handling by at least 50% over the course of a game, due to the increased number of bases, time wise and for anyone with a bad back, than can become significant.

The 80mm large base is very easy to handle and substantially reduces the amount of base handling during play. It looks the nicest when representing line, but is limited in representing other formations and relies on markers to show everything from disorder to being in march column. They do not always integrate well with hex terrain, being harder to fit in the hex with say a building or woods and can look like they are teetering on one end, as though partly floating on air on some terrain such as hills or hedge lined features.

The 40mm base while not a perfect solution, is a good compromise on the short-comings of the other sizes that I have tried. So going with 2 x 40mm bases per infantry and cavalry unit seems the most practical choice.

The unit can be set as a line or attack column, or placed back to back for a square. For march column, I find placing one behind the other and then having a mounted figure in front is sufficient to differentiate the formation from an attack column ( which looks the same, but does not have a single mounted figure in front).

For mechanised forces, I use single 40mm x 20mm bases to represent a rifle section. The linear dispersal of the section strikes me as looking a bit more realistic than a square base and the 40mm base can be loaded with figures and still look right.

Weapon teams such as HMG and mortars seem better mounted individually on half sized bases (20mm x 20mm). My artillery observers are on a small triangular base, just so that they are easily distinguished.

Anti-tank guns are based as though shooting from cover, but this is just to get the gun barrel leaning on something to give it some support and prevent bending from handling (or dropping!). The bases are cut just large enough to take the weapon and associated scenery.

My 10mm vehicles are based and opinion from gamers in general seems split as to whether to base or not. My own experience is that on the table it keeps the vehicles at the correct height in relation to the based infantry and in storage, the bases stop the vehicles from moving and colliding into each other. Vehicle bases are cut to roughly 10mm wider than the actual vehicle (giving 5mm excess each side) and length wise, cut to just a tad longer than the vehicle. Turrets are not glued down, so if the vehicle is dropped, the turret has a chance to fall away unharmed instead of getting mangled