Whats the best way to patch holes drilled in the bottom of a tank?

[theokie]

So I have a 150 gallon (48x24x30) that is drilled for the traditional corner overflow. I want to change it over to an internal coast to coast overflow so I need to decommission the two holes in the bottom of the aquarium.

Whats the best way to do this, should I put in the bulkheads and then just use a threaded plug, or should I have a glass patch cut and silicon that over the holes?

And if I go the glass route, should I go with the same thickness as the bottom of the tank, 1/2" in this case?

Any words of wisdom would be greatly appreciated.