How about going the other way? (FRA - DUS via rail)
We are arriving FRA on DL 48 at 1025am.
Rail Europe looks like there is a train (#610):
1:09PM/13 Sep
Frankfurt Flug FE
2:33PM/13 Sep
Duesseldorf Hbf
1hr 24min
Will there be enough time to retrieve luggage, clear customs, and find our way to this train?