Thanks Guys, been doing more research up until the small hours and starting to get a better undertsanding.
Whats the general rule for frame size vs the actual cutting area? I'm limited for space so I'm hoping that 10' x 5.5 will be enough for 8' x 4. I only ask because I was looking at the linear bearings on ebay and the nearest size I'll be needing are 2750mm which is a fair bit past the actual cutting size.