Hello Johannes,
I included Welter in my night fighter ace list
http://forum.12oclockhigh.net/showthread.php?t=45031
as he argued to have claimed 25 night kills and 2 day kills in the Me 262.
My Eder conjecture stems from
http://www.luftwaffe.cz/eder.html
Dropping him, the next candidates might be me Bär and Rademacher indeed.
But what about Franz Schall ?
Have a nice Saturday,
Michael