What if i set the triggers to =10 ?..
Hmmm... let's try.
According to the wiki, 5 is the max value. also I'm pretty sure that the numbers correspond to the fortress levels (hamlet, city, etc) here.
Yesterday i've modded in "orcs" from OrcMod (size=7 littersize 2:3) and "orxz" that are alike orcs but bigger in size (10), fatty (10), damblock=-1 and child=3 littersize=1:5 (less they eventually somehow don't survive).
Set orcs' triggers to 2-6-5.
Set orxz' triggers to 5-10-15.
All seasons active.
And get an orc siege straight with the first merchants in the first winter - that was a great luck for me as i had only 6 picks and an axe.
That's against 10 orc wrestlers, 4 maces and 1 swordmaster (or swordlord?).
Merchants helped me survive but almost died out, the one survivor retreat off the map crying loud in horror. ;-)
In spring i get next siege, now of orxz, somewhat 12-15 wrestlers, 5-8 spears and 1 macelord.
They come just a second after the human caravan and wipe them all out including the diplomat before i even ensign all my 7.
And the foe were defeated by the stonetraps corridor and bone crossbows with orc bone bolts (as i don't even find magma pipe to smelt orc iron and have no trees to fuel industry).
Then was a year of repose.
And now i'm sitting locked in my cave, as they come to visit me at once from different sides, TWO hords of orcs (each of ~15 warriors), THREE hords of orxz (3*15) - they bastards don't fight with each other.
And a human cohort on the other side of the map, just modestly awaiting for their queue in the farthest corner.
So i think maybe 5 isn't maximum...
I wonder if i get another orc/orxz siege next year in addiction to these? (as i won't able to destroy these sieges in this year)
UPDATE: One horde of orxz crushed the human siege.
Another 2 hordes of orxz have arrived.
And i've managed to defend myself with a whole array of stonetraps and trap-bridges.
96 corpses and 203 body parts on the map, some of them already rot to bones.
Uh. Every dwarf is wounded, i'm lucky two of them still can walk, and other's don't bleed.
I'm dread to even imagine what will be next year...