I would avoid any method that interrupts the surface of your top. I attached from underneath. Search here on router table sag. There is a lot of info on proper support for tops that will help. After experiencing sag despite support in addition to the manufacturer's original design for my top I did something like this to correct it (sorry for the crude diagram):
The support ribs are doubled 3/4" BB ply on end forming 2-1/2" tall support rails. These have through holes and I simply used coarse thread washer head screws and screwed directly into the router table top from underneath every 8" or so. All the usual rules for drilling and screwing MDF apply. I had to mount and dismount the table several times to shim despite using a straight edge to adjust the ribs before mounting.
P.s. I wouldn't be concerned about the flatness of your top until you get it mounted. I like MDF for tops as it is very stable but it flexes a lot if poorly supported ;-)
Last edited by glenn bradley; 12-23-2008 at 10:08 PM.
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