In case you want another option, here is a clamp that I designed to use with my 2 part plastic y-bed & only uses 2 drill holes in the bed.
Just print the clamp part only from this thing: http://www.thingiverse.com/thing:824227
It looks like this.
Y-AxisBeltClamp.jpg
Here is also one that will use 2 of the square holes and the center hole on the wooden build plate.
http://www.thingiverse.com/thing:824458