hi why not make up a couple heavy duty Security Bollards with a base plate that can be bolted down with chemset with a sleeve welded on top for the bollard then slip over then bolt it, would be alot easyer than climbing under the car everytime for a u-bolt, wouldnt take much to cutt through it.... or you could cut up your new floor concrete the bollards in
atleast it will slow them down
anyway awesome thread look forward to future posts
http://www.castlehardware.com/catalog/6 ... 35_130.013