Ummm...sorry I am so late to this party, I just noticed the thread!
I was wondering, if you are going to use the 1/35th Lion Roar rockets anyway, why not use the entire Nebelwerfer kit? Lion Roar Nebelwerfer review.
The tubes are in brass, they provide PE rails, all the little wiring bits and the tubes are even drilled for the fasteners for an extremely detailed build. All you would have to do is cut down the tubes and rails. It is a bit spendy, but it might be possible to get 12 rockets from it, or at least 6.
Here is another review with some pics of a real Nebelwerfer that might be handy:
PMMS review.