I think I could have made mine to hold more eggs but I don't think I'll need to hatch more than a dozen at a time. I'd have to build more coops, runs ..........
The paper towel idea is pretty good, I've been stumped about how to keep the packing peanuts in there (duct tape?) think I might try the towels instead.
I think the drain plug hole (with the wiring running thru it) will work as a vent on that side, and I drilled a 1/2" hole near the top on the other end, should be good air exchange.
I am installing the fan on the inside of the lid blowing down on the light bulb, across the bottom water tray and up to the egg area.
The pc fan I have does still have the sticker on the back saying it's 12 volt, so I searched through all my adapters and found one the same voltage. It's an old fan, and I was worried about it burning out in mid hatch, so I ordered a new one from Office Depot for $3, they delivered it the next day UPS free shipping. Couldn't beat that deal!
I haven't gotten it all put together yet, but I do have all the parts and where I plan to put them with the holes needed already all drilled. Just gotta start screwing parts in tomorrow.