the teak effect looks great, I have the same rack on my D1, and I used a sheet of walk way board that looks alot like the chicken coop flooring mentioned earlier. Its the stuff with grit stuck to the top sor safety on elevated walkways (looks like a waffle)
It is Fibre glass (I think) and cut to fit where I want it, and secured with exhaust clamps to the rack.
I checked out the waffle board/fiberglass grating for the floor of my roof rack. I drove to Henderson, Nevada (Las Vegas) to the American Grating warehouse. I found some good grating/waffle board that was 1/2 inch deep and 1 1/2 inch square mesh and light grey/charcoal color. The grating was impressive, and I would have attached it with plastic ties most likely. The floor would have cost about $400, and I would have to do some trimming of the fiberglass to make it fit like a glove. It was certainly possible to do the floor that way. I did not like the fact that the grating would make it hard to attach rubber bungies to the metal frame of the roof rack under the grating. I wanted full and unrestriced access to all of the steel framework to have lots of flexibility in the way I attach my loads on the roof rack.
I ultimately decided to use the composite boards, and if they don't work out long term, I may go to the fiberglass grating for the floor. The website for American Grating is:
http://amgrating.com
American Grating has offcuts in their warehouse, and for less than $100 you can get waffleboard to use as bridging ladders and sand ladders. They will happily sell you a pair. When I go up to Nevada next time, I intend to pick up at least two waffleboard bridging ladders.