Install glass overflow with small stocked tank

[HillbillyYoda]

I'm having my tank drilled this weekend. There will be two 3/4" drains (one being an emergency). How would I go about applying silicone for an internal glass overflow. I have two small clowns and LR. I will be dropping the water level of course. I would like to give the silicone a few days to cure. Am I answering my own question or does anyone have any advice for this? Also, is using a cut piece of pvc to brace underneath the box an ok deal?

[peppie]

If it were me I would buy a small rubber maid tote to house the clowns and rock for 4 to 5 days while I made the mods to the DT.