Dude, that sucks big time. I wouldn't be too worried about chassis deflection, though you might want to check for some hole elongation & be extra careful to look for the possiblity of cracks occuring around the drilled holes.
I'd take it up with the city where the manhole cover is located.
Thank you guys!
I went to Paul's (Mega Monster Garage) today and with Bill Wilner's valuable help we managed to remove the middle section.
It seems that the damage is limited only to the butterfly brace...
I was thinking to go against the city but for $300 probably doesn't worth to do it...what do you think?