I would start with thinking about the frame support. It looks like you are counting on the OSB sheets to make sure that your table is level, but I think that will not be nearly enough. If you put this on a table top with a warp, twist or bend, the X drives will skew accordingly.
Check out Nook Industries site; their screw catalog has speed tables to estimate max linear speed without whipping; it depends on how you want to secure the ends of the screws.
It is hard to make more detailed comments on a design without more dimensions.