Undercoating can weigh as much as 10 Lbs for one fender alone.

I've removed about 60Lbs or so of the stuff from my car's entire underbelly including the rear end well and all four wheel housings. It was as thick as an 1/2 inch in some places. The trick to removing it easier is to ironically pick a hot day to be under, but in the shade to soften the stuff. It's easier and a little cleaner with a torch as compared to paint remover/solvent applications. Yes, the seam sealer can be messy and thick in most places.