In my modifying the cabinetry to maximize space I realized I would need to move a couple holes Escape made for a gas line and the refrigerator drain. The fridge drain hole can be clearly seen, so I endeavoured to measure up the layout there.
I got a total thickness near 13/16". This includes from the top down, 1/16" of vinyl flooring, 1/2" of plywood, and the remaining 1/4" was a thin layer of resin on a fairly thick fibreglass shell. The purpose of the resin is to level the rough surface of the shell while providing bonding for the plywood.
In drilling my hole through the floor with a sharp 3/4" space bit, it chewed through the top like butter, but once it hit the resin and fibreglass, it went slow, kinda grinding its way through. Very tough stuff.