I can report that I've broken the front off my squared chassis. I run the K factory front tower, the night I broke the chassis I had 1 pretty big accident...Got bombed by another car coming off the side of a nearby jump, hit me head on as I came flat out down the straight! Car survived completely at the time...with the excepetion of the bodyshell being ripped clean off.
I crashed a little later on, with what I thought was a soft one, but it took the front of the chassis off
That night I'd also fitted an extra bit of bling...ali & carbon front top plate, which meant the front shock tower was mounted in a totally metal construction...leaving the chassis to bear the full brunt of any impact.
I've since swapped back to the plastic top plate, but still run the K factory tower.
Expensive night, but I'm not worried about it's durability, it was 'one of those things'. I'd of broken the B4 chassis as well I'm 100% sure. Love the car too much to jump ship!