I did indeed do exactly this.
I used a 32x80 inch door I got cheap from the local Habitat Restore. This provided a 24x65 inch usable cutting area.
I have enlarged it once when I wanted to do some cuts longer than the 65", and I’m considering options now to enlarge for full sheet…
I do think the solid core door approach is a great easy way to get a working Lowrider. I just keep coming up with new project ideas that require (or at least would benefit from) a larger working area. 8^)
I would still start with the door if I were doing it again. It was an easy way to get a working Lowrider, that fit in my space. A full sheet machine is going to need to be fold-able or something to fit in my shop space. That is a project in itself, and I’m still mulling over the issues and options.