@mrmcbeefycakes I've done valley setups a bunch. But never with this number of AI's. I'm thinking there are some oddities around the terrain that could cause the path finding to take longer.
I agree with Jip that you don't 'really' need that many AI per game. I'm not sure if you are struggling to be challenged with a lower number. If you are I'd be remiss to mention the amazing m28 AI available on faf. You certainly won't need more than 1 per player to get a good fight.
If you have a couple of the replay links from where you saw bad stuttering I can take a look as it's possible there is a pathing loop happening that needs to be looked at.