IS-IS Flat Network Size

Hello, I'm wondering what some practical/real experiences have been with building out a large flat IS-IS network. I've read a lot of threads on conjecture and older docs on what the vendors recommend but haven't found anything yet or real world examples. Two questions, 1) Is anyone running a flat IS-IS L2 network with approx 300 routers? If not, what is the higher end you've seen? 2) On aggregation routers, what is the upper end of IS-IS adj to downstream routers? Would agg routers with approx 100 connections be an issue moving to IS-IS with the addition of keeping track of that many adj? Thanks.