I am familiar with the flex agents, and this painter has been doing work along time. These fenders do not appear to be fiberglass, but SMC material for which he was familiar with. Now with all this being said, a sharp force hit from the backside could cause enough deformation that the tensile strength of the paint could not stand, causing the crack.
To me, the bigger concern is that there is nothing to take the brunt of high speed wheel debris. I spent a lot of time on gravel this past week and suspect this is what caused my failure. A inner panel or Linex could go a long way toward prevention.
Either way, I will discuss when I am there and we’ll get it fixed.
1995 F350 CC DRW XLT 2WD 5-Spd w/ BD Exhaust Brake 225K Mi, HyperMax Stage 2 Kit, HyperMax EGT & Boost Gauges, Riffraff / Tymar Intake, HyperMax Intercooler, HyperMax 330HP chip, Adrealine HPOP & Braided Lines, Melling M208 LPOP and HyperMax 4" Exhaust. Coming Soon: DP-Tuner F-6 and custom electric fuel system.