If you have to, you can always "lap" a 2x3 or 2x4 pine stud along one edge of the table, to pick up an additional 1.5 inches of safety space.
You may want to reconsider a little, and go with the 054 curves. Once it is built, you will never "notice" that it isn't 060, and you will have safety space and extra room for scenery if you like. Trying to fit a square peg into a round hole will be frustrating, . . . and you may never be happy with just the tiny safety margin on the edge of the outer tracks.
The 060 curves will also create issues all around the track if you have switch motors (like the Lionel 022) that must jut out 4 inches or so from the track. You would have to place all of these motors on the interior side of your loops and curves, and this could seriously crowd a siding or interior track run, forcing these tracks to be a full 6 inches apart. And, having all of the motor units on the inside of the track may just look strange.
A compromise to 054 would solve all of these problems, while giving up very little.
Hope this helps.
Mannyrock
