Does anyone have experience with retrofitting their 14 inch bandsaw with the 12 inch height/cut extension?

Yes. I've had mine for decades. I got it to saw duck decoy blanks and
needed the increased height. I'm running a 3/4 horse motor, and Iturra
suggests that I put in a 1 1/2 HP. (I haven't found one cheap enough
yet.)

I also suggest you get the Iturra catalog and booklet. (No connection
etc.) It's full of goodies to enhance your saw.

Joel