Battle scale is ~10,000 ships on 1/2 ship settings. AI usually spawning 4-6 carriers carrying 400-800 ships a piece. About 3k ships friendly, about 4.5k in the air AI + carriers.
Majority of ships are mirrors, youngling commandos, and Missile Frigs from the AI. My lot is a mixed mess of spawners, snipers, a ton of turret, 60 or so riot starships, standard triangle, parasites, and a few other mixed additional ships.
If I can find a good way to drop a save file off and attach here I will.
Slowdowns are variable. If I do *nothing* it'll stop for ~20 seconds, then start up again, and freeze again say 15-20 seconds later. This will happen until fleet mass gets down to around 8000 across all parties. If I try to do anything it can nearly perma-freeze (I've been trying to figure out what the primary causes are), particularly if I get rambunctious.