'half as long AGAIN' does look somewhat more dated than 'half AGAIN as long'.
It is a regional thing, so it seems.
Прикол, что оборот проходит с пометой British в MWD:
Это again в (half/twice, etc.) as much/many again следует понимать, кяп, как "сверху".half as much/many again as idiom
British
—used to say that the size or amount of one thing is 50 percent more than another
If 100 people were expected and 150 came, half as many people came again as were expected.
This dress costs half as much again as that one.