don't they add more vibration and such?
yeah- but i suppose it depends how crazy ur prepared to go. the whole process obviously gets fairly expensive (with the usual diminishing returns) after you've hole-sawed every internal panel as far as you dare, replaced every piece of non-structural metal and glass with plastic or FRP, swapped parts for billet this/forged and CNC-machined that, replaced every nut and washer with titanium and alu equivalents where possible....