I found out some more about "Agil" as a solution to "Gjennomtrekk". "Gjennomtrekk" can be translated into "stretch" in English. And stretch can be translated into "fleksibel" (flexible) in Norwegian. So there is apparently some sort of connection between the two words, but pretty far-fetched in my opinion. Still doesn't solve the problem that "Gjennomtrekk" is a noun, while "agil" is an adjective.
pibbur who may, depending on his mood, examine the problem a bit mor, but who will never stop working on devious crossword puzzles.