Azusa OHV Mud Pit last year.
A rock hidden under the mud damaged my subframe, oil pan, tranmission crossmember (made shifting extremely difficult because of shift assembly was lodged), Catalytic converter, and downpipe. Definitely need more/thicker underbody protection.
Was it worth it? Absolutely! Seeing the boggers stop in their tracks to see a little subaru hauling a$$ through the mud was priceless.