I got Dortmund under 1.5 1st half for today
i assume you mean the game total.
i think that s very dangerous bet. Dortmund is in general more of an over team this year, especially away where they won all 3 games 3-1.
but the main questionmark is Köln. Köln is unpredictable this season how they show up.everytime they are able to play solid defense they are getting points and games go under (3 of 3 games)..everytime they loose the games are going over (3 of 4 losses went over). problem is you cannot say in general that they dont have a solid defense (they had one of the best in league last season), but this season they either play on the normal solid level or having unexcuable mistakes.
go for Köln is similar with the under bet, going Dortmund should hit the over.
therefore it s hard to predict a total for this game, even more difficult a first half total (i couldnt find any particular tendency for either team on that).
personally i am not quite decided on the side, but if line moves even further towards dortmund, i might jump small on Köln.