No you won't. The front sway bar is high (above the control arms) on the Miata. I've experienced a sraping of my front subframe/engine tray on my stock heigh Miata. It sucks, heh.
I've always liked the rocker panels in black on the M1 Miatas. I've been contemplating painting them black on mine. I'm trying to keep a black and white color scheme, so I think it may look quite good.
2.5" off the ground? I'd think it'd be hard to see daylight under, if it were THAT low...heehee...I don't see the skirts - but think you mean rocker panels, eh?