I don't know about the 03, but this is how i did the Recaro's on my 1302.
Hacked off the Recaro seat mounting points. Welded some flat bar across the slider portion of the stock seats, then hacked off the frame/sliders. Welded this square of slider portion to bottom of Recaro seat. Works well. Sliders move back/forth, seat moves up/down in height as stock, and its sits low on the pan. I hate seeing some seats installs that are soo high your mellon can touch the headliner.
Seats are from a '98 VR6 "driver's edition" GTI: