Surfacing slabs longer than CNC

[nopoint]

I have access to a cnc router that has a 4x8 bed and was thinking about using it to surface some longer slabs. Specifically some 10' burr oak that is nearly 4' wide. Anyone have tips on keeping the slab on the same plane as its moved ahead for the remaining length? Hate to flip these things over too many times. Sawn at 3 and 4" they are beasty heavy. Should be lighter now after air drying for 4 years. Maybe secure some runners to the bottom of the slab to start out to have a flatter reference? Anyone doing anything like this? Would like to surface both sides. 

[blackhawk]

I've done this a few times successfully on my 4x8 CNC.  I flatten the first 8 feet and then I flip the slab over and do the same on the other side. Next, I get four 1.5-2" wide boards that are exactly the same thickness and put the boards under the previously flattened portion just like stickers in a lumber stack.  I shift the slab on the boards to flatten the remaining 2 feet.  Then you have to flip the slab repeat for the other side.  This method only creates 1 extra flip.  

If you need to remove a good bit of material on the 1st 8 feet of either side, watch to be sure that your flattening bit doesn't hit against the ridge of the un-flattened area.  This only comes into play if you are using a carbide insert bit where inserts are at an angle and that ridge exceeds the cutting depth of your cutter.

[nopoint]

That makes sense. Thank You. Now to dig them out and give it a shot.