ramtheory-- the overflow wasnt that hard, it was very time consuming, i order a diamond bit from hong kong $11.99 including shipping, then logiktest came over and we stood the tank on end, got a ladder out, used some plumbers putty to make a little dam to keep the bit submersed in water and just kept grinding away with the drill all three holes took about 3 hours (1/2 in glass) resting in between holes. then i had the glass cut at st. Charles glass and siliconed them in place using 2x4's for support to keep it from falling.
this replaced using a cpr overflow box, a great decision on this build.