All the machines I have for cutting stone have hex bar and rollers. which are on top rails and of course have easy access But the table is also on large V rails to load the stone one of them is worn so I don't get the Accuracy I need to Make stone profiles But its still great for straight cuts and 90 degrees . it only takes 15 mins to change the rails except on the Bottom as the rolling table weighs a ton.
all the Hex rail machines with rails underneath do have difficulty changing and the gantry must be Supported when they are lifted off. But my attitude is if it needs changed Its done its work about 4 hours per rail to change only because they are bolted with Sunken heads. even mild steel rails last a lot of cuts and justifys the rail change