Regarding " Plate F" cars. Currently no cars exceeding " Plate C" can make it past the bridges near the Perth Amboy NJT station on the NJCL.
Its a classic " What came first, the Chicken or the Egg" story. Nobody on the Southern or Freehold needs Plate F, because nobody on the Southern and Freehold can get Plate F. Woodhaven and Builders would probably love to have Plate F cars. Plywood is frequently moved in bigger "F" cars, it will allow the consignee to receive more product in less railcars, reducing potential demurrage charges.
On the DD/DRRV, three lumber mills now have access to "F" cars. Also two different sites for refers/insulated high cars are now available and seem to be doing good business. Something the Class One was not willing to do.
Nobody here can really say what the immediate benefit of increasing the clearance would be. My opinion would be in order to survive and potentially grow a traffic base you have to increase clearance.