Hi, Lew!
Two significant ideas regarding AACW Artillery have recently been developed on these forums. You should know about these, because they're far from obvious.
Here's the first.
For a long time, many people had believed that there was a limit of four artillery per division. Common knowledge said that more than that was a waste. Not long ago, it was discovered that this was a myth, and that the limitations of the number of artillery pieces which could be effectively used in a division was defined by what is called "frontage", rather than any hard-coded number, in the game code. Even so, there were some common misconceptions about what those ideas implied. Some people (myself included) were initially ecstatic at the idea of large numbers of powerful artillery in Divisions.
Jabberwock provided research in the thread, "Frontage", which actually provided the exact numbers of "how many, of what" could be effectively used, given the particulars of terrain and weather. Major Tom followed this with a thread of his own about Frontage, going into much greater depth. If anything, the seemingly inescapable conclusion of the data presented seemed to be that
much,
much more artillery could be used than had been previously imagined. I decided it would be a good thing to consider what the limits might be. I presented the pros and cons of divisional artillery in the thread, "Artillery Divisions". Based upon that research, I privately came to the conclusion that artillery in a division should number between five and seven, with eight or more being the rare exception.
The second significant "discovery" was that there are essentially two artillery ranges of engagement: "Long Range", where a weapon's range is of consequence; and "Short Range", where a weapon's maximum range is of
no consequence. The surprising part was in the details: "Long Range" engagements
only occur in clear terrain, in fair weather. (Clear Terrain being defined as clear/desert/prairie.) With such a variety of weather and terrain as the game provides, it seems that Long Range engagements are the exception, rather than the rule.
Each unit in the game is based upon what is called a "model". Those models are defined in the database which can be found in the modding sub-forums. Our forum's current discussion of Artillery is centered (mostly) on two ideas.
The first involves the models of Columbiads and Rodmans. Currently, there's a consensus that the current models should either have movement penalties (because weapons of such power would be heavier and slower), or be redefined as something else that's more historic. For the Rodman, it has been proposed that the model be redefined as a "3 inch ordnance rifle". This suggestion is controversial. [
Edit 5 Jun 09: After reviewing the "columbiad/rodman" thread, I realize that this was your suggestion. I think your arguments were good ones, and some of your considerations have been used by our AACW beta team in the process of redefining and re-evaluating the current Rodman model.

]
The second involves adding new artillery units. For example, one proposal is for a 24 lb howitzer. This is mildly controversial: on one hand, some believe that this weapon is already included in the "siege weapons" battery; a different line of thinking believes that this would be a useful and versatile addition to the AACW arsenal.
Anyway, we've learned a lot, but there's a lot that's yet to be learned. And regarding your artillery analysis... I'd like to be among the first to commend your effort, and encourage you to do more!
I'll discuss the particulars of your spreadsheet in a different post.