I don't think the supports are original. They are extremley strong but its just steel painted with black enamal. They work fine as they are, and its another thing that can be replaced later on.
I was also worried about screwing through the floor, but after searching the forum, it seems this is what most people have done.
Originally Posted by MustRib
I see you cut off the spray dodger then !
I actually glued down that inch or so flap that remains onto the top of the tube.
I left quite alot on while I was cutting the main part off, then went back and trimmed it neatly and glued it down. I now want to finish this off with seam tape, when I find some!