Speaking of rocket tubes, are they modeled to produce more drag then the xmas tree racks that are on the 38L and later 47s like the D40 and N?
Yes, the 'bazooka' tubes do add weight/drag to the P38J airframe.
The Christmas tree racks on the P38L do not give any weight penalty what so ever after all the rockets have been fired. I haven't been able to determine if there is any drag related to them, but it isn't noticeable if there is.