I thought about this. But its strength properties arnt my need. Its magnetic properties are. It just lays on the bed of the xcarve and gets clameped through along with the plywood wasteboard and g10 sheet that i wish to cut. And the 3-4mm error area is very small. The rest is less than 1-2mm. Not to mention 4 may be a slight exaggeration now that I think about it, i was eyeballing it with a level. Its not that bad
Then the 1inch cube magnets take over the clamping needs for thin flexible material that vibrates when crazy large portions are removed. And i can move them during the cut. And they are very strong and clamp very tightly.
And i over cut rather deap to make my bits last longer as g10 chews up the fishtails of my cutters and wears them out fast. Mutch faster than the burs on the bit. Which are still normally in great shape.
So overcut like that is bad for a vacuum table.