Battle magic/reverse communions

[Flop]

Alright, so I have more questions, this time regarding magic and communions. I've been reading Baalz' guide, and I'm wondering about the section on reverse communions:

2 or 3 masters then as many cheap slaves as you can muster. Your masters will cast Power of the Spheres then whatever other booster is appropriate (Phoenix Power, etc). For air spells you can use the third master to cast Storm so that air power is an option. Now, all your slaves have been boosted 2 levels, so they can cast fun things like falling fire, thunderstrike, etc. Even lowly S1 mages are now capable of Soul Slaying.

It sounds good, but I'm not sure I understand some of the mechanics. As I understand, a communion slave casting spells, will not benefit from the communion (no extra levels, for the purposes of casting and fatigue), so in order to boost them two levels, so using the example given above, how does an S1 mage gain two levels? The only possibilities I can see, is if one of the masters casts Light of the Northern Star (or is carrying the banner), or if multiple castings of Power of the Spheres stack, in which case I've been playing the game wrong.

Could someone clear this up?

Also, I've been trying a few reverse communions, but my slaves often go off script and start using defensive buffs on themselves, in the second round, before the masters have a chance to do it for them. I'm not sure if this has to do with the range of the scripted spells (it certainly might), or if there are any tricks I need to learn, regarding the scripting of mages. In any case, I'd like it if someone could tell me the rough distance between two starting armies, and what sort of spells would be good to use for the first few rounds, before they close.

Finally, again regarding range, I usually put my mages at the very back of my army, on the left edge of the setup screen. It occurs to me that I might as well put them just behind the rear-most troops, which would usually put them somewhere around the middle of the setup screen. Any thoughts on this?

Thanks.