Made it to 600m on the FSR with a Prius, there’s a handful of easy water bars that can be easily managed with care and technique without bottoming out. Not worth pushing further without clearance.

Drove as far as the turnoff for Mt. Cheam. Littered with large potholes filled with water as well as waterbars every 50 meters in some spots. A minor culvert washout that almost any moderate clearance 4x4 should be able to get through. No major washouts or challenges on this road, just annoyingly rough.