>> the top two just cracked.
Yup! Most drill bits skitter or crack plastic. That 90-degree spade bit works great, through.
My very dear SO saw me dithering about buying a cheap soldering iron for melting holes, and got me a really nice 200-Watt wood-burning soldering tool with adjustable temperature. One nice thing about melting holes is that the plastic "beads up" around the hole and reinforces it.
