IMO unless the amount of filler (thickness) is reduced, the cracking will come back regardless. A bit of hammer and dolly work will do wonders to minimize the amount of filler required to get things smooth.
See this is the crazy part, I can't even wrap my mind around how they were able to make this much bondo work with certain parts on the truck, I'm afraid if I strip it all down I'll have trouble even getting these parts to fit right again.
for example:
Driver's side headlamp area I'm afraid of what I'll be left with after taking all this bondo off!!
