POR-15 has a body putty that can seal the holes and build back up the thickness. The stuff hardens up just like steel. Stuff is called Resto GRIP. Follow link:
http://www.prp-porstore.com/merchant.mvc?Screen=PROD&Product_Code=RG&Category_Code=Fillers
http://www.prp-porstore.com/merchant.mvc?Screen=PROD&Product_Code=RG&Category_Code=Fillers