Some surfboards are up to 12 feet in length, the only way to cut these boards would be a belt driven or chain driven mechanism I will try to cover this topic in the future with a sample machine and pictures. An example of a machine larger then 8 foot would be a surfboard foam cutter. Belt driven machines are usually 8' and longer but require the use of micro-stepping. Another way is to move to a chain or belt driven design. One way to overcome this problem is to move to a larger diameter lead screw. The problem with a long lead screw is that because it its own mass, it will 'wobble' in higher speeds. Keep in mind that for longer travel you will need a longer lead screw. The design can be modified to almost any size.
The first prototype was made out of wood, but didn't look 'professional' enough, so I decided to go with a more robust design made of steel. Most parts can be found in your local hardware store, like Home Depot.
