Mine granularity

[Shyrka]

I have some questions relating mine deployment. I think the bigger mine is a Large mine (20 kT) with 4 Mine warhead III (damage 300) so it has 4 X 300 = 1200 damage. Let's call it BigMine (BM). The SmallMine(SM) would be a Small Mine (10 kT) with a Mine Warhead I (damage 100) so it has damage 100.

The cost for a BM is 600M + 240R, and for a SM 150M + 20R.

To reach the 1200 damage of a BM it is needed 12 SM that will cost 1800M + 240R so they not worth.

BUT they has an advantage: "granularity". An small escort (150 kT) that hits a minefield of a single BM will be destroyed, but also the minefield. The expensive BM is wasted (1200 minus more or less 150 equals to 1050 damage wasted) IMHO. But if this minefield is composed of 12 SM, only 2 of them will explode destroying the escort and leaving still a minefield of 10 mines capable of destroying another 5 escorts. I think this is interesting, and I never use the Large mine chassis. Have this been asked before?I'm wrong? Any thoughs?