Thanks for the comment, that makes a lot of sense.
I had always thought of cannons as being highly valuable and "rare"....but as you say, they were 1,000s of them so maybe not like I used to think.
I have only today worked out the artillery crew numbers from the HW OOB result, taking the start number of INF and CAV away from the total start strength leaves arty crew numbers.......roughly 20-25 per gun.