"We do however know that the DA40 was joining crosswind and had just crossed the upwind numbers of the active runway(20). The Vans was, it is believed, on circuits."
So, from this, and foregoing information, I understand that each aircraft could have been somewhat "out of position" relative to what would normally be expected? The DA40 was crossing the runway centerline farther along the Van's takeoff path than the Van might have expected (and could not see down, as a wing could block that view)? The Van's perhaps had the capability of a climb rate after liftoff, which would enable it to be higher than normal along it's departure path, and maybe even had a pitch attitude which would lessen the forward field of view?