If anybody is interested in doing the straps mod I'll post the part numbers below. The stock floor liner should have four round indentions (aprox 45 mm) on the underside of it....this is where you will have to drill 25mm holes for the mounts. Its actually a really inexpensive and easy mod to do and you will probably have parts left over since the mounts are sold in packs of ten.
Mount, retaining strap upper section x 4 51478146943
Mount, retaining strap lower section x 4 51478146941
Tension strap x2 51478136450
http://www.realoem.com/bmw/showparts...=51&fg=65&hl=4