12 12"s won't work..... doesn't sound good, especially in a clamshell.
Nahhh I'm just yankin' you. Listen to Boom and to Blade Ice. They have done this more than once. I had these SAME questions as you when I built my clamshell, and yes- I initially tried to use ported box design to build the box -and I did to a degree- it got me in the ball park.
I Thought I tuned my box to around 35 hz. I THOUGHT. Much much much lower. Clamshells are tricky like that, but nothing like the visual wow factor.
Tuned in!