Unfortunately it's a lot more complicated than that for modern panniers. The latches for the QR style panniers like Blackburns and Ortliebs and other similar brands tend to wrap right around or over the rack bars. The flat bar across the top of the FL-1 stops this. It takes a fair bit of modification to hack away the bar so the latches will work, without weakening the structure of the rack too much. I only did it because I got the FL-1 for a ludicrous price and I have all the tools needed.
The FL-1 would still work OK with the old style hook and strap type panniers though.