you can get some timber strips from hardware or 10mm half round or square and glue this to the cabinet bottom . either remove the old strip or reglue existing trim/ply if okay. i did remake the rear of a gottlieb cab using 20mm ply but its a bit of a job because you need to rebate it along the corners. or put a post out for a cab im sure someone near you would have that era gottlieb cabinet.