Hello Gilles,
Do you check the Volksbund database (
http://www.volksbund.de/graebersuche.html) for these men ?
They are listed with the following death places:
Wirth: St.Pons
Reile and Wolber: südl St.Pons (south of St.Pons)
Keunecke:Condades sö. St.Pons (southeast of St.Pons)
The last location being the smallest place is probably the most precise. But you probably have the crash place allready...