i have built both fiberboard and plexiglass/lexan boards and from my own personal experience the extra money spent up front for sheet metal will more then pay itself back in longevity of the board...especially with a field cover on it which will dampen the vibrations even more. the metal, barring a major accident will last a lifetime as where fiber board and lexan have ALOT of be carefull precautions that go with them like water..heat etc.
Good luck with your build coach.
