Hi Scott, You can certainly do it but it will require some wood working skill. It also depends on what arm you want to mount. Some mount through a larger hole and the wire exits the arm from beneath an example would be the SME arms. Others mount on top of the turntable with an RCA junction box mount on top or on the back of the turntable such as the VPI arms. Either way you can deal with it. Because all tone arms are going to leave cosmetic damage of some sort to the plinth I would make a removable tonearm board. I would make it out of solid surface material like Corian. You could use MDF but then you'd have to finish it. The tonearm board will cover any existing problems and can be drilled according to the spindle to pivot spec for the arm. the VPI has a thicker platter and solid surface material is only 1/2 inch thick. This will give you plenty of room. You have plenty of real estate to work with and you could mount just about anything.
Pick an arm and get a piece of solid surface material from Home Depot. Then I would be happy to help. I'm actually a licensed Corian installer. The only stuff I have in the shop right now is white which I think would look rather odd on a Classic.
