Port Posistions on a cab

Can the port posistions on speaker cab alter the sound drastically, are they critcal?

I was thinking of making a single 12" version of the SMT212 for smaller venues and also for portability and wasn't sure if moving the ports for the rear chamber to the bottom of the cab (so the speaker mount panel would not have any ports but, the bottom of the rear chamber would be ported from one rectangular hole at the bottom end of the rear chamber which, could also double as a handle?)

Or would it be wiser to port the rear chamber from the back of the cab again near the bottom?

Thanks guys, Jim.

In that situation no effect imo

Thanks Nick. I thought that it would not be an issue. Cheers.

if the port distance from the horn and the diaprham is the same, don't change so much, but the ports must be inside the horn.

Thanks Bitzo, I see what you mean. If it was a reflex cab then it would not be so important? smiley20