I am researching F/L (then F/O) P E Ipsen at the moment. I can confirm that he was the Ipsen sharing the victory on 15/5. I have transcribed the relevant part of the 237 Sqn ORB for a list of Ipsen's operations on my website
http://danishww2pilots.dk/sorties.php?id=1055
The topic has been touch before on the forum
http://forum.12oclockhigh.net/showthread.php?p=198247
Evidence suggest a Do 17, rather than Do 217.
Regards
Mikkel Plannthin