Kitwe,
I stand corrected then.
There are, as I'm sure you know, no guages to inform the pilot of drop tank status, and tapping on the walk-round is of dubious value; the only cure I can think of is to be freshly topped up !
BTW, what was the purpose of said trials ? As far as I know 438 wasn't carrying any particular stores; maybe HUDCASS development ?
DZ