Slotted head shells and adjustable bases are supplied to accommodate various cartridges. The idea being to maintain the proper overhang dictated by the effective length and offset of the arm. The pivot to spindle spec is chosen to get you in the ball park. The cartridges geometry will dictate the exact location.
Using threaded inserts in wood is fine in this context if done right. Wood is soft. The threads of the insert will displace the wood upwards causing a dimple. The tonearm will then not lay flat on the arm board. You have to counter sink them then plane the surface flat. What you are doing is converting a machine screw to a wood screw.
Running machine screws through the arm board and bolting the tonearm down is a bad idea. Again, wood is soft and will expand and contract with humidity and the seasons. Through bolts will always loosen even if you use washers. Of course this is not true for metal and synthetic materials. These you can drill and tap. Best for wood is wood screws. Just size them appropriately and predrill the holes. As fsonic relates the exact pivot to spindle distance is not critical but if you get to far off you may not be able to adjust the arm for certain cartridges.
Using threaded inserts in wood is fine in this context if done right. Wood is soft. The threads of the insert will displace the wood upwards causing a dimple. The tonearm will then not lay flat on the arm board. You have to counter sink them then plane the surface flat. What you are doing is converting a machine screw to a wood screw.
Running machine screws through the arm board and bolting the tonearm down is a bad idea. Again, wood is soft and will expand and contract with humidity and the seasons. Through bolts will always loosen even if you use washers. Of course this is not true for metal and synthetic materials. These you can drill and tap. Best for wood is wood screws. Just size them appropriately and predrill the holes. As fsonic relates the exact pivot to spindle distance is not critical but if you get to far off you may not be able to adjust the arm for certain cartridges.