FreeSki what size hole did you drill? It's no big deal bro, just go get yourself a bulkhead fitting. My coolers are RDWC, and now I'm setting up a med grow for a friend with 16 coolers all connected in an undercurrent system.
I cut a hole in each cooler's lid for pot, then a 2 more holes drilled in the lid for feed lines, another 3 holes in the side. 1 DWC for drain, 1 for air, and 1 for rez changing drain. You folks who cut no holes in your coolers, how do you flush your res? Unless you get a cooler with a spigot. You have to take all your shit out and then go dump your cooler upside down somewhere? That's ridiculous.
No offence to anyone who does it super simple, that might work for your little closet grow, but you're not gonna be topping off 20 different coolers and checking PH and nutes in every single one. At some point, you have to link your coolers together and go with RDWC or UC to connect them all. This makes for a way more efficient system with much more DO, your plants will love you for it.
I hate to see people shitting on someone for taking things one step further. RDWC or UC is better than any number of non-connected containers, so get off this guy's back and help him out, he's taking cooler growing to another level.
I'll take some pics of my RDWC cooler closet grow when the lights come on tonight FreeSki. I'll also snap some of my 16 cooler UC setup once it's built.
P.S. Hot-Glue and a glue gun is an amazing adhesive/sealant for us folk. It's a thermoplastic, you just heat it up until liquid, apply, then it hardens. There are no solvents or offgas curing with Hot-Glue, so it's perfectly safe for use with plants.