A piece of angle steel as shown above will be used to fasten the two longer pieces in the center of the car. It was modified slightly to fit snugly against the larger pieces by grinding the inside angle to a sharp angle rather than rounded as most are when they are manufactured. It was initially planned to weld the pieces together, although subsequent information obtained suggested that bolting would be better considering the repeated stresses that would occur as part of a train. It was felt that welds would be vulnerable to breaking more easily.
So, back to our friend the mag drill. Drilling was a little tricky because the width of the steel was such that the magnet couldn't hold optimally, but it worked.
Like so.
Meanwhile, Tom was making a prototype bracket to refasten the cross-pieces between the inner and intermediate sills that had been removed, cutting the mortises. These should be quite stable after tensioning the tie rods across the car.