Hi Landmeister,
If Bw(X) is double based with another Bw, then the rear Bw can shoot in support of the front rank bow.
Also, the rear rank bow provides the front rank a +1 factor in close combat in an enemy bound. Bw(X) is treated as Sp in close combat.
In DBMM, there is a big difference between "aiding" and "support". If you look carefully you will notice that for Shooting (Distance Combat?), rear ranks "aid" the front. But in Close Combat they give "support".
I think we should try and use the same language, otherwise people may think when you say "Bw support" you are only talking about Close Combat, not Distance Combat.
Hope this helps,
JohnG