There is mention of using drop tanks in an attack here:
https://books.google.com/books?id=Tm...rafing&f=false
The narration is by James L McCubbin (44-15672, MACR 12506, 364th FG). The "Lt Berry" he refers to is actually "Lt Jack T Barrie" (44-13657, MACR 12502, 364th FG). In the MACR for Barrie there is an eyewitness statement by Francis X Radley. Radley mentions dropping his tanks "as bombs" on the train being attacked. Then Lt Berrie followed him, also dropping his tanks. Lt Berrie was hit during his attack.
All the examples found so far seem to occur in February, 1945. I wonder if this technique was being widely discussed in Fighter Groups at the time and it appears perhaps several groups were actually trying it.