A little Astra Militarum update

At the moment I am working on building my first Field Ordnance Battery unit for the Walpurgian 3rd. This is basically artillery pieces mounted on wheels that needs to be pulled in to battle. This is the biggestweapons the Walpurgian 3rd has that is not self propelled.

At the moment I have two sets (each set has two artillery pieces), but I know I will get more over time. This is a new set for this year for the Astra Militarum, so I don't yet know how it is best to field them but that is something I am working on finding out. They come with three different options: Bombast field guns (basically a regular cannon), Malleus rocket launcher (multiple barrels) and a heavy lascannon (looks like it is a bigger version of the lascannon you get with the heavy weapon squads). Each cannon has a crew of 3 with a loader, a spotter and a gunner. The two teams form what is called a Field Ordnance Battery. 

What I am trying to find out is how many sergeants you have in a unit. Is it one for each gun, or is it one for each battery? And do you usually field two similar artillery pieces in a battery, or do you field two different set-ups? I am leaning towards fielding two artillery pieces with the same set-up as one unit, and put one sergeant in charge of that unit. Then I will eventually (as I get more guns) put up to 3 batteries together as one bigger unit with a Veteran sergeant (or any other sergent rank) in charge of 6 artillery pieces and their 3 regular sergeants. But I will see as I build the crew for the first unit if I find out something more about this. I might also ask my friendly Warhammer store staff if they know.

So far I have built the two cannons of the first battery and their gunners. I have made one Bombast and one Malleus and I plan to build the same setup for the second batch. Then when I get a third box I will make two heavy lascannons. Next time I get to sit down and work on my minis will be on Friday, and then I will build the rest of the crew. 

I mentioned earlier that I have built Usula Creed, and I am also trying to find out how I will field her in the army. My highest ranking officer is the figure for Usaker E. Creeed and I plan to keep it that way, but I would like to have Ursula in a regular sot as a high ranking officer, then if I shuld happen to play an official tournament or something (not very likely) then she can be the general. I might make her as Major Belle Boyd, the commander for the 2nd Armored artillery units, if not I will have to think up a higher ranking officer position where I can put her.